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Navas 28800 Modem FAQTM [Modem Picture]

(Answers to Frequently Asked Questions)

Copyright 1995-1996 The Navas GroupSM, All Rights Reserved.
Permission is granted to copy for private non-commercial use only.
Send mirror and commercial license inquiries to info@NavasGrp.Dublin.CA.US.

Posted as <http://www.aimnet.com/~jnavas/modem/faq.html>. Updated Wednesday, January 22, 1997.

Breaking News

Copies of this document in either hypertext (HTML) or plain text format may be obtained by email from an "agora" server (e.g., agora@info.lanic.utexas.edu or agora@dna.affrc.go.jp) or from web-mail. For information on agora, send an email message to an agora server with a body of "help"; for information on web-mail, send a blank email message to web-mail@ebay.com.

Please note: The author has no present connection with any modem company (other than as a customer), and does not endorse the products of any company. This information was compiled by the author and is provided as a public service. Neither the author nor any organization mentioned herein are responsible for any errors or omissions, or for any consequential problems that might result. USE AT YOUR OWN RISK.

Please note: The author does not have the time to give individual technical support, so please do not email requests for assistance. Instead, post them to Usenet. Thank you.

Email comments and suggestions to JNavas@NavasGrp.Dublin.CA.US


Contents

Section I:

Section II: Modem Companies on the Internet

Button [The Navas Group home page]


Why don't I get 28800 bps (or more) on my connections? [updated 10/27/96]

(If you see a connection speed of 38400, 57600, or 115200, don't be fooled -- that is the serial port speed between your computer and your modem, not the speed between your modem and the remote modem. To report the modem-to-modem speed, your modem probably needs a different initialization string. Consult your documentation.) [new 7/27/96]

Note: Reported initial connect speeds won't necessarily be dependable or even comparable from modem to modem or location to location. The reason is that V.34 modems can (and often do) speed shift up and down after the initial connection, and do so in a manner that is dependent on the particular connection as well as the particular equipment (including firmware versions) at each end. (See "What are "fall-back" and "fall-forward"?") Some modems connect at a more conservative speed and then quickly upshift as conditions allow; other modems connect at a more aggressive speed only to quickly downshift (or worse, lose performance due to excessive errors). Another problem is that software may report the receive speed for certain modems and the transmit speed for other modems, which can be substantially different. (See "What are split/asymmetric speeds?") Unfortunately, it is not possible to monitor the actual modem speed during the connection for most modems. Regardless, the only thing that really counts is net throughput, which can be measured by many communications applications. [new 10/27/96]

If you consistently connect at 26400 or above, there may not be much that you can do to go faster -- it's simply not possible to achieve the highest V.34 speeds on many phone circuits. (This is not false modem advertising -- 28800 modems are designed to wring as much speed out of the actual real-world connection as possible, and 28800 or higher speed is only possible on a near-perfect connection.)

If you consistently connect at lower speeds (e.g., 24000 or even 21600), there may still not be much that you can do, but you can at least try the following:

A final note: Add-on noise filters will not help -- they are the modem equivalent of snake oil. Your 28800 modem already has all the filtering it can use. An add-on filter will do nothing at best, and it may well make things worse.

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What's a good download speed? [new 1/22/97]

Here are some general, rough guidelines. Bear in mind that data download speed is affected by many things other than modem-to-modem connection speed, including: the load on the remote system; the speed of any network links (e.g., Internet congestion); the speed of the local computer-to-modem port (e.g., serial port speed); the load on the local system; quality of the communications software; and the transfer protocol (e.g., ZMODEM or FTP).

TYPICAL DOWNLOAD SPEEDS
MODEM CONNECTION
SPEED (BPS)
UNCOMPRESSIBLE DATA
(e.g., .ZIP) SPEED (CPS)
COMPRESSIBLE DATA
(e.g., text) SPEED (CPS)
14400
1600
3200
21600
2400
4800
24000
2670
5330
26400
2930
5870
28800
3200
6400
31200
3470
6930
33600
3730
7470
36000
4000
8000
40000
4440
8890
44000
4890
9780
48000
5330
10670
52000
5780
11560
56000
6220
12440
64000
7110
14220

Notes:

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What's the difference between V.FC and V.34? What's next? [updated 10/27/96]

V.FC
A proprietary specification for speeds up to 28800 bps, based on an early draft of the V.34 standard, that was rushed to market by modem chipset leader Rockwell International. It works reasonably well, but lacks the sophistication and robustness of V.34; for example, V.FC does not support split speeds. Many (but not all) V.FC modems are upgradable to V.34, but the modem typically has to be returned to the manufacturer for a "datapump" change. V.FC-only modems will not connect above 14400 bps to V.34 modems that lack V.FC support. With the advent of V.34, V.FC is rapidly fading as modems are upgraded. In the opinion of the author there is now little or no reason to get a modem that has V.FC but not V.34, although until V.FC fades completely there will still be a significant advantage to a modem that supports both V.34 and V.FC.
V.34 [updated 10/27/96]
A true international standard for speeds up to 33600 bps (more realistically 28800 bps) that is more sophisticated and robust than V.FC. Some but not all V.34 implementations support optional features like 31200 and 33600 speeds and/or split speeds for transmit and receive. V.34 is rapidly replacing V.FC in the marketplace. V.34-only modems will not connect above 14400 bps to V.FC-only modems. In the opinion of the author V.34 is clearly the modem standard of choice. It may well prove to be the last widely-supported analog modem standard.
56 Kbps [updated 10/16/96]
Rockwell Semiconductor Systems (along with a number of its customers), USRobotics, and Lucent Technologies have announced plans to introduce modems that work over conventional phone lines at speeds up to 56 Kbps. See "What are 56K modems?"
28800-33600 fax
Fax is currently limited to 14400 bps over dialup analog phone lines (Group III V.17). Efforts are underway to define a 28800-33600 bps fax specification, which would probably be widely adopted. However, general availability is probably a few years away.
Voice
See "What are "voice" modems?"
Plug and Play
See "What is Plug and Play"
ISDN
See "What is ISDN?"
"Cable modems"
See What are "cable modems?"
ADSL/SDSL/HDSL
See "What are ADSL, SDSL, and HDSL?"
Universal Serial Bus
A better way to connect a modem to your computer than the conventional UART or parallel port. (See "What is a UART?") Expected to become a standard feature of many chipsets and motherboards (e.g., those manufactured by Intel) and operating systems (e.g., Windows 95), although USB is not yet available. (See "Universal Serial Bus Home Page" and Intel's "USB Interactive Tour")

See also "Modems: the make-it-happen machines for the ultimately wired of the 90's"

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What are 56K modems? [updated 12/24/96]

Rockwell Semiconductor Systems (along with a number of its OEM customers), USRobotics, Lucent Technologies, and Motorola Information Systems Group, have announced plans to introduce modems that work over conventional phone lines at speeds up to 56 Kbps. See:

There are several catches however:

As for the looming competitive battle between Rockwell and USRobotics, the latter appears to be in the stronger position for two reasons:

  1. USR has a large market position among Internet Service Providers (ISPs), with a substantial installed base that can be easily upgraded to 56K ("x2") technology.
  2. USR claims that all of its modems currently in distribution will be easily upgradable to 56K technology. (While choosing such a modem would seem to be a good way to get ready for 56K deployment, the higher speed may well only be possible when connecting to an ISP that installs USR-brand digital "x2" technology.)

An interesting possible fallout is that the new 56K technology may finally force down the price of ISDN. (See "What is ISDN?")

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What are split/asymmetric speeds?

In the past, most standard modems were only capable of transmitting and receiving at the same speed. (The exceptions were proprietary modems such as the USR HST that used greatly different transmit and receive speeds.) Since most connections were made at the maximum speed, there was little reason to support different transmit and receive speeds.

With the advent of speeds up to 28800 bps that is no longer true. It's now quite common to have a connection where at least one (and often both) speeds must be limited to less than 28800 bps, and it's not uncommon to find that a connection will support faster speed in one direction than the other. (One reason is that send and receive channels are separated for transmission between telephone switching offices.)

Having been designed to optimize performance over a wide variety of conditions, V.34 includes an optional specification for asymmetric (differing or split) transmit and receive speeds. For example, a connection might support a transmit speed of 28800 bps but a receive speed of only 26400 bps; without split speed, the speed in both directions would have to be limited to 26400 bps. For this reason split speed capability is a worthwhile and desirable feature.

Not all V.34-compliant modems support split speeds. For example, at the time of this writing most "glue 'n go" Rockwell V.34 clones, do not support split speeds. On the other hand, others, including all USR V.34 modems (Sportster 28800/33600 as well as the Courier V.34), Diamond/Supra, and Motorola, do support split speeds.

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What is Selective Reject (SREJ)?

Selective Reject (SREJ) is an optional, advanced LAPM (V.42) error correction capability that allows the receiving modem to request retransmission of a given block while continuing to receive later blocks; i.e., to receive the retransmission late (out of order). Without it, the entire transmission has to start over at the retransmitted block, which can result in later blocks being resent unnecessarily. Hence, Selective Reject can improve throughput where there is a significant error rate, particularly over links with long delays (e.g., satellite links).

Not all modems support Selective Reject, which is typically found only in high-end products.

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Do I need a 16550 UART? What is a UART?

A UART (an acronym for Universal Asynchronous Receiver-Transmitter) is simply an interface chip. Your computer needs one to "talk" over a serial connection to serial devices such as serial printers and modems. Each serial device needs a UART chip to "talk" to your computer, even modems that are installed inside your computer.

In computer terms the UART is very old technology. We continue to use them because we own so much software that depends on there being a specific kind of UART. Efforts to replace the UART and its particular serial architecture are ongoing (e.g., Universal Serial Bus), but it's doubtful that the UART will be replaced anytime soon.

There are many types of UART chips, but only two main types that are used in IBM-compatible personal computers:

  1. 8250/16450. Major weaknesses of the 8250 and 16450 are a lack of built-in flow control, and buffers that can only hold a single character. This means that the UART must be promptly serviced by the system processor each time a character is received, or that character will be wiped out by the following character, a condition called "overrun." (See "Why am I getting CRC errors (overruns) when downloading?")
  2. 16550. A substantial advance over the 8250/16450, the 16550 has both a fully 8250-compatible mode and a newer mode that provides 16-character FIFO (an acronym for First In, First Out) buffers. When the old mode is enabled, it works just like an 8250; when the newer mode is enabled, the FIFO buffers greatly extend the time available for responding to incoming characters. The receive FIFO buffer has a variable threshold that can be set to values of 1, 4, 8, or 14 characters, with higher numbers giving less time to respond before the 16-character FIFO buffer is full; on the other hand, higher numbers can give slightly better performance, by allowing the system to process incoming characters in larger "chunks." A good rule of thumb is a threshold of 8 characters. (See "What about third-party comm drivers for Windows?") Most (but not all) internal modems come with a 16550 UART.

Some internal modems emulate UARTs with on-board logic rather than using actual UART chips; these products can provide more effective buffering than a conventional UART. More advanced UARTs (e.g., 32-character FIFO buffers, built-in flow control) are becoming available, but they are generally not needed. Parallel modem interfaces and the Hayes ESP card are alternatives to UARTs, but they require special drivers and provide no significant advantage over the 16550A in the opinion of the author.

In general, a single-task operating system like MS-DOS can get by with an 8250/16450 UART with serial port speeds of 19200-57600 bps (depending on the speed of the system processor) and well-written software. This is usually adequate for even a 28800 bps modem. However, a multitasking operating system like Windows, OS/2, or UNIX, will usually need a 16550 UART. (Nevertheless, if you are stuck with an 8250/16450, you can probably still use a 28800 bps modem if you are careful.)

You can tell what kind of UART chip you have by running Microsoft's MSD (which comes with Windows), being sure to run it outside of Windows. (The reason is that Windows can hide the true state of the UART from MSD.)

The Universal Serial Bus (USB) is a better way to connect a modem to your computer than the conventional UART or parallel port. USB is expected to become a standard feature of many chipsets and motherboards (e.g., those manufactured by Intel) and operating systems (e.g., Windows 95), although it is not yet available. (See "Universal Serial Bus Home Page")

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Where can I get a 16550 UART? [updated 4/24/96]

An extensive, excellent list of multiport serial cards has been compiled by the amateur radio site ve7tcp.ampr.org. [new 4/24/96]

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Why am I getting CRC errors (overruns)? [updated 9/7/96]

CRC errors (e.g., as reported by ZMODEM), particularly when downloading, are usually a sign of overrun (incoming data that is lost because the computer is unable to process it in time). Overrun can result from a variety of causes. The following are suggestions on how to avoid CRC/overrun errors (particularly in Windows 3.1):

  1. Use a 16550A UART. (See "Do I need a 16550 UART? What is a UART?" and "Why does Windows lock up when I access my modem?") Note that most, but not all, internal modems have a 16550.
  2. Use hardware flow control, and make sure it is working properly. This applies both to your modem and to your comm software. If you experience overrun while uploading, then you almost certainly have a flow control problem in your comm software and/or modem configuration.
  3. If you are running anything other than the standard Windows VGA driver, switch to the standard VGA driver and see if that affects your problems -- certain video drivers are known to interfere with communications. (See "Where can I get updated video drivers?")
  4. If you determine that your video driver is causing overruns:
    1. If your video card uses a recent S3 chipset (e.g., 864, 964, or 968), there may be an option in the video driver to set "Bus-throttle=On" (usually Off by default) in the [display] section of SYSTEM.INI, which may well solve the problem. ("Bus-throttle=On" may slightly reduce speed as measured by benchmarks, but the difference will probably not be noticeable in the real world.) Contact the manufacturer of your video card. (Note: Generic S3 video drivers are available from S3. Unfortunately, they do not work on all S3-based video cards.) [updated 3/29/96]
    2. If your video card is a PCI type and made by Matrox, try adding PCIChipSet=1 to the [MGA.DRV] section of SYSTEM.INI, which may well solve the problem. (Add the section header if it does not already exist.) If it does solve the problem, check with Matrox for an updated video driver. [new 6/13/96]
  5. If possible, use 32-bit disk access under standard Windows, as well as 32-bit File Access under Windows for Workgroups. If not, be sure you have a current version of a quality BIOS and/or disk driver.
  6. Watch out for poorly-written firmware and/or device drivers for local bus IDE interfaces, particularly in multi-sector mode. Obtain the latest versions. (See "Where can I get updated disk/SCSI drivers?") You may be able to alleviate an overrun problem by switching modes and/or reducing the number of sectors per transfer.
  7. Are you using a SCSI drive? Certain SCSI drivers can cause problems. Obtain the latest versions. (See "Where can I get updated disk/SCSI drivers?")
  8. Disable write caching on your download disk drive. (Read caching should be OK.)
    * With the current SMARTDRV (i.e., standard Windows, or Windows for Wordgroups without 32-bit File Access), the /X parameter disables all write caching. You can also disable write caching on individual drives. (See "SMARTDrive Drive Letter Parameters Should Not Contain a Colon")
    * With 32-bit File Access under Windows for Workgroups, put the following in the [386Enh] section of your SYSTEM.INI file:
    ForceLazyOff=<drives>
    where <drives> is a drive letter string; e.g., ForceLazyOff=C for drive C only, or ForceLazyOff=CD for drives C and D. (See "How to Disable Write Caching for the 32-Bit File System")
  9. If you are using Procomm Plus for Windows 2.xx, set "DropRTSAroundDiskWrites=1" in your PW2.INI file. (This won't help if you cache writes.)
  10. Beware of TSRs, especially network TSRs. Try booting your system as clean as possible to see if that helps.
  11. Watch out for certain memory managers; e.g., the use of QEMM "Stealth" may cause problems.
  12. Put your modem on COM2 if possible, rather than COM1, especially if you are using a serial mouse, because COM2 has higher interrupt priority than COM1. Even better is to use a "high" IRQ (2/9, 10-12) which has higher interrupt priority than either COM1 or COM2. (See "Where can I get a 16550 UART?") [updated 8/30/96]
  13. Under Windows, put the following in the [386Enh] section of your SYSTEM.INI file:
    MinTimeslice=20
    WinTimeslice=100,50
    COMnFIFO=1
    COMnBuffer=1024
    where n is the number of your modem COM port (e.g., COM2FIFO=1 and COM2Buffer=1024). The COMnFIFO statement won't help until you get a 16550A UART, but it won't hurt in the meantime.
    Note: The only legal values for COMnFIFO are 0 and 1. (See "Windows Support of the 16550 UART")
  14. Do not use Microsoft's PC speaker sound driver! Get a cheap sound card instead. (The Logitech Factory outlet in Fremont, California, 800/231-7717, is a good place to get a cheap sound card.)
  15. The Creative Labs Sound Blaster 16/AWE 32 driver bundled with the original release of Windows 95 can cause CRC errors, and should be replaced with an updated version. [new 9/7/96]
  16. Watch out for an IRQ conflict. (You normally cannot use both COM1 and COM3, or COM2 and COM4, at the same time.)
  17. On a portable or "green" machine, you should also try disabling the power management features, which can sometimes "kick in" and interfere with data communications.
  18. Disable any screen savers, which can interfere with data communications.
  19. Don't run your serial port any faster than necessary. Marketing hype notwithstanding, there's rarely any need to go faster than 38.4 Kbps with a 14.4 Kbps modem, or 57.6 Kbps with a 28.8 Kbps modem. Caveat: With an acknowledgment protocol (e.g., XMODEM), as opposed to a streaming protocol (e.g., ZMODEM), a higher serial port speed can improve the response time. (See "Measurement of DTE Rate Latency")
  20. Try a third-party replacement for COMM.DRV. (See What about third-party comm drivers for Windows?)
  21. Switch to Windows for Workgroups or Windows 95, which have a better serial architecture than standard Windows 3.x.
  22. With a 16550 UART (See "Do I need a 16550 UART? What is a UART?") under regular Windows and a third-party comm driver (e.g., WFXCOMM.DRV) or Windows for Workgroups or Windows 95, try dropping the receive FIFO trigger level. For example, where n is the number of your modem COM port:
    * WFXCOMM.DRV (default 14): ComnRXSize=8 (e.g., Com1RXSize=8). Recommended setting.
    * Windows for Workgroups (default 8): COMnRxTRIGGER=4 (e.g., COM1RxTRIGGER=4).
    Legal receive FIFO trigger values are 14, 8, 4, and 1. The normal recommended value is 8. You should not go down to 1 unless you are really desperate.

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Why is my modem getting NO DIAL TONE? [updated 10/7/96]

  1. The most obvious cause is that you've neglected to plug your telephone line into your modem. Double check to make sure. Or the telephone cable may be bad -- test it on a regular telephone.
  2. A common problem is plugging your telephone line into the wrong jack on your modem. Many modems have two jacks, one for the telephone line and one for a telephone handset. On some of these modems (e.g., USRobotics), you won't be able to get a dial tone or otherwise use the modem if you plug the telephone line into the telephone handset jack. Double check to make sure.
  3. Another common problem is that some other device on the same telephone line (e.g., a telephone answering machine) is off-hook. Double check to make sure that all other devices are on-hook.
  4. There may be a problem on your telephone line. Make sure that you can get a dial tone on a telephone handset connected to and through your modem when the modem (or computer in the case of an internal modem) is turned off.
  5. Many voicemail systems use a "stutter" dial tone or beeping when you pick up the phone to indicate that you have voicemail waiting. These unexpected sounds can make the modem think there is no dial tone. If you must use the modem on a line with these voicemail or similar sounds, you can try the following workarounds: [new 10/7/96]
    1. Increase the amount of time that the modem waits for dial tone by setting the number of seconds to wait in register S6 (e.g., S6=5).
    2. Lower the Xn setting to an odd number value to make the modem ignore dial tone and dial blindly (e.g., X3 instead of X4, or even X1).
  6. Your modem may not be designed for the phone system in the country in which you are trying to use it. As a workaround, try lowering the Xn setting as described above.

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What's wrong with my dialup SLIP/PPP connection? [updated 10/27/96]

  1. Make absolutely sure that there is one and only one WINSOCK.DLL on your system, and that it is the right one.
  2. Make sure that the directory (e.g., C:\TRUMPET) for your dialup SLIP/PPP package (e.g., Trumpet Winsock, aka TCPMAN) is in your DOS PATH environment variable.
  3. Try the following settings in your dialup SLIP/PPP package:

For more SLIP/PPP help see "Any Trumpet Winsock tips?" and "Troubleshooting Reference."

Note: There is no significant performance difference between SLIP and PPP. (See "SLIP vs PPP Performance Comparison" and "Performance Issues")

The author recommends the following Winsock applications (all of which are freeware or shareware):

For more Winsock application information see:

You may be able to run dialup SLIP/PPP from a UNIX shell account with The Internet Adapter (TIA). Even when your Internet Service Provider offers a SLIP/PPP option, it may be cheaper to run TIA from a shell account. TIA is commercial but inexpensive. A freeware alternative is SLiRP. For more information on TIA and SLiRP see "SLiRP/TIA and Trumpet Winsock Setup Reference." (Usenet alt.dcom.slip-emulators)

Advanced/Professional Users

A good tool for debugging SLIP/PPP protocol problems is SerialView from Klos Technologies. [new 10/27/96]

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Any Trumpet Winsock tips? [updated 10/11/96]

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Where can I get updated video drivers? [updated 12/1/96]

Updated video drivers may help to correct CRC/overrun errors. (See "Why am I getting CRC errors (overruns)?") Updated drivers are available at:

Note: Only those companies that have drivers available for download are listed.

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Where can I get updated disk/SCSI drivers? [updated 9/07/96]

Updated disk and/or SCSI drivers may help to correct CRC/overrun errors. (See "Why am I getting CRC errors (overruns)?") Updated drivers are available at:

Note: Only those companies that have drivers available for download are listed.

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Why 1024 bytes for the Windows COM buffer?

The buffer size is mostly a flow control issue. When the buffer fills up above the "high water mark" (e.g., 75%), a Windows comm driver asserts receive flow control; then when it drops below the "low water mark" (e.g., 25%) a Windows comm driver releases receive flow control. (A Windows comm application should have nothing to do with flow control. DOS applications, on the other hand, do not use the Windows comm driver and so must do their own flow control.)

For Windows applications then the only serious issue is that the size of the buffer between the "high water mark" and buffer-full must be big enough to give the local modem time to respond to flow control being asserted -- there is inevitably a certain amount of "dribble," but it's usually no more than about 10-20 characters, for which even the default 128-byte buffer should be adequate. For performance you want the buffer large enough for the Windows application to be able to process incoming data in reasonable sized chunks. (You also want the modem to respond to flow control being released before the buffer is drained by the application, although this is much less important due to modem buffering.) Thus if multitasking is going on, a somewhat larger buffer than the default (e.g., 256-1024) may improve performance. The higher end of the range accommodates a typical (YMODEM/ZMODEM) block. Beyond that point diminishing returns set in rapidly.

For DOS applications the buffer size is more important, since the DOS application is responsible for flow control and takes much longer to respond than a Windows comm driver. That's why it's a good idea to have a receive buffer as big as a typical (YMODEM/ZMODEM) block (i.e., 1024 bytes). The alternative is to turn the buffer off completely and give the DOS application direct access to the COM port by setting a buffer size of 0.

On the transmit side (where there's no flow control concern) the only consideration is performance -- you want the buffer to be big enough so that it doesn't drain to empty when the application is unable to respond fast enough to refill it. The default 128-byte buffer will drain in only 22 ms at 5760 cps, which is less than a single multitasking timeslice. A 1024-byte buffer takes 178 ms to drain, which is normally sufficient; above that point diminishing returns set in rapidly. One reason is that modem buffering can make up for (short) times that the transmit buffer drains to empty. And if you make the transmit buffer too large, it can introduce timing problems (due to the "long" buffer drain time) with DOS applications and with poorly written Windows applications.

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What is "retraining"?

What are "fall-back" and "fall-forward"?

It's very important to properly distinguish between (a) retraining and (b) fall-back/forward. They are frequently confused but they are not the same thing. If you turn on the modem speaker with M2 you can easily hear the difference.

RETRAINING

Retraining is like the initial training -- several seconds where the modems probe the line in order to configure themselves (equalization, nonlinear coding, pre-emphasis, pre-coding, shaping, mapping, etc.). Either modem can request a retrain, but the retrain will only occur if the other modem grants it. You can hear the distinctive training sounds if the modem speaker is on. During the several seconds of retraining no data can flow. Because of that we want the modems to only retrain when truly necessary, as when line conditions have changed significantly and permanently, something that is usually rare. Retraining may not necessarily result in a higher speed. Excessive retrains can therefore be a serious problem.

FALL-BACK/FORWARD

Fall-back/forward is simple speed shifting that is relatively quick, so we would like the modems to fall back when needed to keep the error rate low, and fall forward when possible to improve throughput. With the modem speaker on you will hear only a small beep or blip in the carrier hiss. If a noise burst causes a fall-back, we want the modems to fall-forward as soon as the burst is gone. What we don't want is for the modems to ping-pong back and forth between two speeds, because that would result in lower throughput than simply remaining at the lower speed. Again, fall-back/forward can be requested by either modem, but will only occur if the other modem permits it.

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How do I set a speed greater than 19200 bps in Windows?

You can set a speed faster than 19200 in the Windows Control Panel by simply typing it in. However, there is almost never a need to do so -- almost all Windows comm applications set their own serial port speed. The settings in the Control Panel are primarily for devices attached to the serial port; e.g., printers. (See "Control Panel Serial Port Settings Are for Printing Only")

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What about third-party comm drivers for Windows?

Despite "urban legends" to the contrary, the standard Windows 3.1 COMM.DRV is capable of supporting high-speed modems on a reasonably fast system, and does support the 16550 FIFO. (See "Windows Support of the 16550 UART") However, it does have three limitations:

  1. It does not use the transmit FIFO. This rarely makes any difference for data, but can be a problem for Class 1 fax timing above 9,600 bps.
  2. The receive FIFO threshold is fixed at 14 bytes, which leaves only 2 bytes before overrun occurs. Dropping the receive threshold to 8 bytes (or even lower) may help to reduce overruns. For that you need a third-party comm driver.
  3. DOS comm programs running under Windows 386 Enhanced Mode are fooled into thinking that the COM port only has a 16450 UART. This can cause problems, particularly with poorly-written DOS comm programs (i.e., those that do not drain the UART buffer on each receive interrupt). The alternative is to give the DOS application direct access to the COM port (see "Why 1024 bytes for the Windows COM buffer?") or, better yet, upgrade to Windows for Workgroups 3.11 or Windows 95.

Also despite "urban legends" to the contrary, COMM.DRV supports speeds up to 256,000 bps, hardware permitting, including 115,200 bps. (See "Setting Baud Rates in Windows 3.1") How fast you can go will depend on your hardware. With only an 8250 or 16450 UART, you may not be able to go faster than 19,200 bps without overrun; with a 16550 UART and a reasonably fast system, you should be able to go up to 57,600 bps, or even 115,200 bps. 57,600 bps is normally adequate for even a 28,800 bps modem. Caveat: With an acknowledgment protocol (e.g., XMODEM), as opposed to a streaming protocol (e.g., ZMODEM), a higher serial port speed can improve the response time. (See "Measurement of DTE Rate Latency")

Third-party comm drivers include the freeware:

CYBERCOM.DRV
WFXCOMM.DRV (from Symantec, particularly recommended for use with WinFax)

Third-party drivers are not needed for and should not be used with Windows for Workgroups 3.11 or Windows 95, which have a better comm architecture than standard Windows. An upgrade to Windows for Workgroups 3.11 or Windows 95 is probably the best way to improve Windows communications. (See "Any other Windows tips?") Third-party Windows drivers should also not be used with OS/2 (Warp).

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How can I share a modem between data and WinFax?

  1. Symantec WinComm PRO can seamlessly share a modem with Symantec WinFax PRO. With WinFax PRO set to automatically answer the telephone, WinComm PRO will turn off WinFax PRO auto-answer to dial out, and turn WinFax PRO auto-answer back on when it is through with the modem. The two programs may be purchased together in a discounted bundle called the Symantec Comm Suite.
  2. With other data comm programs you can use WfListen, a program that will shut down Symantec WinFax when you start your data comm program, and then restart WinFax when you shut down your data comm program, all automatically. Shareware. (A companion program, wfStatus, modifies the WinFax icon to show whether it's ready to receive faxes or not. Also shareware.)
  3. Another alternative is KingComm, a commercial virtual comm port driver that allows multiple comm apps to share the same modem.
  4. Multi-Tech provides a proprietary "Virtual Modem" comm driver for Windows with certain modems that will reportedly route incoming data and fax calls to appropriate applications. However, it does not support the 16550 FIFO buffers, a serious drawback. (See "Do I need a 16550 UART? What is a UART?")

Note: Except for Multi-Tech, these alternatives do not have the ability to automatically detect and properly route incoming data and fax calls. For that you need a modem that supports incoming Call Discrimination (also called "Adaptive Answer" or "Call Select"), as well as data and fax comm software which support that capability (e.g., WinFax PRO 7.0 for Windows 95 [see "How can I use a single phone for fax/data/voice?"] or Procomm Plus for Windows 2.xx).

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How can I display the status of an internal modem under Windows? [updated 1/3/97]

Windows 3.x:
ModemSta displays an animated icon replica or larger indicator displays of modem's front panel. Several 3D looks, with customizable colors. For use with internal, external and PCMCIA modems. Modem initialization, logging of incoming calls and connections, additional status info, show communications settings, generation of sounds at comm events. Can also monitor parallel ports. Unfortunately, ModemSta has been withdrawn from shareware. [updated 1/3/97]
Windows 95: [new 6/6/96]
The System Monitor accessory that comes with Windows 95 has a wealth of hidden capabilities, among them the ability to measure Dial-Up Networking performance in real time. See System Monitor under "Any Windows 95 tips?"

Note: It is not possible to continuously display the modem-to-modem speed of an internal modem. (Some drivers and applications display data throughput, but that is not the same thing.) The reason is that you have to have to escape the modem to command mode and issue a special command, if available, which interrupts the flow of data. (See "Any other USRobotics tips?")

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Why does Windows lock up when I access my modem?

The most common cause of this problem is a 16550-compatible chip that isn't fully compatible. Typically this is seen on Pentium systems with serial ports integrated on the motherboard, but it can also happen with add-on cards, particularly "multi-I/O" cards based on popular SMC chips. (See "PC Hangs While Running a Communications Application" and "16550 UART FIFO Support under Windows NT")

Warning: Although Microsoft specifically identifies the SMC '665 chip as the problem, the author has personally verified that a problem also exists in the SMC '666 chip (FDC37C666GT). Furthermore, although the original FIFO problem is reportedly fixed in current chip production, the author has personally verified that a problem (perhaps a different problem) still exists as of August 1995. The author has also personally verified that:

The only fully effective workaround is to disable the FIFO buffers (as described above). For this reason the author does not currently recommend products that use SMC "multi-I/O" chips.

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Why can't I get back on-line after I escape to command mode?

While on-line you escape your modem to command mode with "+++", and then try to get back into data mode with ATO, but the remote system no longer responds. You have to break the connection to recover.

What's probably happening is that your "+++" escape code is being echoed by the remote system back to the remote modem, throwing it into command mode as well, a state from which you cannot recover short of disconnecting. It really shouldn't be happening, because any BBS SYSOP or Internet Provider worthy of the name should either disable the escape sequence or at least change it to an unusual value. But all too many don't.

The solution is to use modem register S2 to change your modem escape character. The author uses S2=61 to change the escape character to "=", which is on the same key as "+", making it easy to remember.

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What are the best (data/fax) comm programs for Windows? [updated 4/11/96]

There are several excellent programs, and what is best for one won't necessarily be best for others.

For data comm, the personal favorites of the author are HyperACCESS for Windows (commercial from Hilgraeve) and the near-clone WinComm PRO (commercial from Symantec). Both are extremely powerful while being very easy to use. For those on a budget, there is a freeware version of WinComm called WinComm Lite. (There is also a freeware DOS comm program from Symantec called FreeComm. Neither WinComm Lite nor FreeComm has been reviewed by the author.)

Popular shareware alternatives include:

Softerm Plus (X/Y/ZMODEM with SLIP and TCP/IP)
Telix for Windows
UniCom
WinQVT (VT-220 emulator with X/Y/ZMODEM/Kermit)
WinRamp Lite (w/RIP)
ZCOMM for Windows 95 (telnet plus best ZMODEM) [new 4/11/96]

For fax comm, the personal favorite of the author is WinFax PRO (commercial from Symantec). It integrates well with WinComm PRO, and the two can be purchased in a discounted bundle as the Symantec Comm Suite. (If you experience fax problems with a USR modem, see "Any other USRobotics tips?")

Note: Delrina was acquired by Symantec.

The author does not recommend Version 2.xx of Procomm Plus for Windows (commercial from Datastorm). While version 1.xx evolved into a robust (albeit quirky) data comm program, version 2.xx has suffered from "featuritis" and has been plagued with many problems (e.g., greatly excessive locking of memory below 1 Mb [See "PRB: Avoiding 'Insufficient Memory to Run' Errors"]).

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Why do I sometimes have problems connecting?

See below and also "Any other USR tips?".

Why do I sometimes get abruptly disconnected? [updated 11/14/96]

With a USR 28800 modem, you can determine the technical reason for a disconnect by issuing the ATI6 command immediately after the disconnection. Disconnect reasons are explained in the Courier manual.

If possible, set these options on a phone number-specific basis. With comm apps which lack that capability, you may be able to embed them in the phone number; e.g., "^H^HS27=48DT555-1212". (The two "^H" backspace characters erase the "DT" in an "ATDT" dial command so that the "S27=48" will be accepted, and then the following "DT" replaces the "DT" that was erased; i.e., "ATDT" + "^H^HS27=48DT555-1212" = "ATS27=48DT555-1212".)

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Why do connections sometimes seem to run slower and slower? [updated 10/11/96]

The following is a discussion of the so-called "spiraling death" problem that has been observed on the Sportster 28800 (and sometimes even the Courier V.34), where the modem will fall back over time on certain connections to ever lower speeds.

What we are really concerned with here is fall-forward, not retraining. (See "What is 'retraining'? and What are 'fall-back' and 'fall-forward'?") Retraining is normally a rare event. So the problem is really that the Sportster 28800 sometimes does not fall-forward when it is able to do so. The symptom is that the Sportster 28800 is sometimes observed to fall back to progressively lower speeds without ever being observed to fall forward back to higher speeds. The implication is that line conditions would have permitted a higher speed, which may or may not have been true. (It's impossible to say for sure without elaborate test equipment.)

THE ATO1 CONNECT RESPONSE CONFUSION

Some of the evidence used to support the claim that the Sportster 28800 doesn't fall forward has been that ATO1 (forced retraining) returned the modem to a higher speed. The problem with at least some of these reports is that people have assumed that the CONNECT response to ATO1 reports the new speed after retraining. It doesn't, as should be obvious if you notice that the response appears before the retraining sound (heard with M2) is completed. The response sometimes shows the previous connection speed, and sometimes shows the original connection speed, but never the new speed. The only way to correctly determine the connect speed after retraining is to escape to command mode and use the ATI6 command! (See "Any other USRobotics tips?", "Any Trumpet Winsock tips?", "Why can't I get back on-line after I escape to command mode?", and "Any Windows 95 tips?")

Suppose that a phone connection is such that the Sportster 28800 CONNECTs at a high speed (e.g., 28800), but then falls back to a lower speed (e.g., 24000) due to line conditions. Escape to command-mode followed by ATO1 might well make you think that retraining has returned the modem to the original high speed (due to a CONNECT 28800 response) when it may well not have. Disconnecting and reconnecting could produce the same misleading indications. In other words, these may just be plain old poor connections. The moral here is that you must use ATI6, and only ATI6, to check the current connection speed.

Another problem is that ATO1 may not change the current speed, or may even reduce it, depending on changing line conditions. And it's hard to keep ongoing auto fall-back/forward from confusing the issue (unless you use M2 and listen carefully for the sound of the speed shifts, a small beep or blip in the ongoing carrier hiss). The only way to know for sure whether or not the speed changed is to use ATI6 immediately before and after ATO1.

SPORTSTER PROBLEMS

Does the Sportster 28800 fall-forward automatically or not? From extensive testing (literally hundreds of hours to both USR and non-USR modems) the author concludes that the answer is: often yes, but sometimes no. The author has run many tests where the Sportster 28800 was forced back to (say) 16800, and then it rapidly fall forward to a much higher speed. But the author has also run some tests where it stayed at 16800. This seems to be a function of both line conditions and the modem at the other end of the connection.

Note that this problem is not absolute -- while some users do encounter it on some connections, many users never encounter it.

Another possibly related problem that some have reported with the external Sportster 28800 (not the internal Sportster, and not either type of the Courier) is that adjusting the speaker volume control while on-line causes the modem to fall back. Anecdotal reports suggest that higher connection speeds may be possible if the volume control is turned all the way down before the initial negotiation (and left there). Turning off the speaker with M0 is apparently not effective.

WHAT TO DO [updated 10/11/96]

USR now has a fix for this problem in the form of updated modem firmware. See "Sportster Supervisory Update Information". (Note: the dates in the firmware table are not necessarily the dates of the latest versions.)

While waiting for the fix, here are some workarounds to try:

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Why do my on-line connections "pause"? [new 10/11/96]

You are on-line to a remote system, perhaps a distant system over the Internet or a local bulletin board system (BBS), transferring data or typing in commands, when suddenly communications stops. Then after a few seconds, a few minutes, or possibly even longer, things start flowing again. The question is, what happened? The answer is, it depends. There are a great many things that can cause this kind of pausing, and determining the real cause can often be difficult, sometimes very difficult. Worse, the cause may be out of your direct control. Here is a list of possible causes, tips on how to identify them, and suggestions for ways to deal with them:

Telephone connection problems

Modem error recovery
When a transmission error occurs, error correcting modems will automatically retransmit the affected data. Under normal conditions the retransmission will be brief, but when connections are poor the retransmissions can result in "pauses" that last for many seconds. Certain modems will help you diagnose and/or detect this kind of problem (e.g., with a "link diagnostics" screen, or flashing ARQ or SQ lights). The only way to completely solve this problem is to get better connections (see "Why don't I get 28800 bps (or more) on my connections?"), but it may help to reduce the connection speed (so as to reduce the frequency of errors).
Modem retraining
While modems are retraining due to a poor connection, no data can flow. Although a single retrain lasts only a few seconds, multiple retrains (and other related error recovery) can go on for much longer, up to 30 seconds or more in the author's experience. See "What is 'retraining'?"

Network (Internet) problems

Lost TCP/IP packets
When a TCP/IP network (e.g., the Internet) gets overloaded, the network routers deal with the problem by dropping (discarding) data packets. It then takes time for the sender to notice that the receiver hasn't acknowledged packets that have been sent, and to resend those packets (which may in turn get dropped). The result is a general slowdown in data transmission speed, often with long gaps or "pauses." In extreme cases packet loss can go as high as 30% or more, bringing transmission down to a fitful crawl with nothing flowing most of the time. This problem can be diagnosed with "ping" and "traceroute" tools (the use of which is beyond the scope of this document). The only way to deal with this problem is by complaining to the network administrator, but there may not be much that can be done if the congestion problem is outside of the local network (e.g., elsewhere on the Internet)
Remote server overload
Remote servers can only handle so much load. When the load gets excessive, there is a general slowdown to all those using the server, often with long pauses when the server is busy serving other users. As the Internet grows, this is becoming an ever-increasing problem, particularly for popular sites. The only way to deal with this problem is to access the server when the load is less (e.g., in the wee hours of the morning).
Routing and other problems
Certain networks are adopting packet routing policies, particularly during periods of peak load, that discriminate against certain users, particularly smaller ISPs (Internet Service Providers). At best the network may drop many packets or route them onto slower, more congested links; at worst, the network may refuse to pass them altogether. The only way to deal with this problem is to be sure that your ISP has good connectivity (e.g., multiple "peering" points, multiple "backbone" connections and/or alternate transport providers). In the long run the smaller ISPs may simply be squeezed out.

Computer problems

Flaky serial port (UART)
A flaky serial port (UART) can cause all sorts of communications problems, including both long and short ("pausing") lockups. See "Why does Windows lock up when I access my modem?"
Improper flow control
If flow control is not configured properly in both the comm software and the modem, the result is overruns. These overruns result in lost data, which can cause "pauses" as well as delays due to data retransmission. See "Why am I getting CRC errors (overruns)?"
Hardware conflict
Hardware conflicts are a frequent cause of both long and short ("pausing") lockups, particularly when two COM ports are set to the same I/O address or IRQ. For example, a mouse on COM1 and a modem on COM3 will normally product such a conflict. (Sometimes moving the mouse will cause modem data to flow, but in other cases the modem may work fitfully or not at all.) See "Why am I getting CRC errors (overruns)?"

Software problems

TCP/IP configuration
Improper TCP/IP configuration can lead to packet fragmentation and other problems that may be manifested as "pausing." See "What's wrong with my dialup SLIP/PPP connection?"
Software configuration and interference
Configuration problems in comm software applications can also result in "pausing." The only solution is to ensure that all comm applications are configured properly. It is also possible for two software applications and/or device drivers (particularly network drivers) to interfere with each other enough to cause a "pausing" problem; the only solution is to eliminate (one of) the offending application(s).
Operating system swapping
Sometime the operating system suddenly needs a lot more memory for a given application, and has to swap megabytes of data between memory and a disk drive. On less sophisticated operating systems (e.g., Windows), this can result in a "pause" in communications during the swapping. The symptom of this problem is a large burst of disk activity.

Modem firmware problems

USRobotics Sportster
Certain USRobotics Sportster modems with firmware dated in February and March of 1996 have a firmware timing problem that can cause the modem to "pause" when the modem is being used in an interactive mode on a normal dialup connection, typically when typing commands while connected to a Bulletin Board System (BBS) or asynchronous dialup UNIX shell. The "pause" will clear itself if you wait long enough (up to about a minute). To troubleshoot and correct this problem, see "Sportster Supervisory Update Information". (Note: the dates in the USR firmware table are not necessarily the dates of the latest versions.) For more SRO information see "USRobotics on the Internet". The author recommends that anyone with an affected modem exchange, update, or return it.
Modem interoperability
Incompatibilities between certain modems car result in a variety of problems, including "pausing." If disabling V.42 (and falling back to MNP) causes the problem(s) to go away, then you probably have an interoperability problem. A firmware upgrade that corrects the problem may be available for your modem. See "Which modem companies have a full Internet presence?"

The simplest and most effective way to deal with a modem problem is to return the modem to the dealer from whom you bought it for refund, credit, or exchange. (Even when you are outside of the normal return period, many dealers will still take back the modem for credit or exchange, particularly if you are persistent.)

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Why does my Windows 95 Internet run at half-speed? [updated 10/18/96]

The MaxMTU Fix [updated 10/18/96]

Have you found that your Internet file transfers (e.g., downloads) are very slow, in the range of 1,000-1,600 characters per second, even on a 28800 modem connection? It may just be Internet overload; on the other hand it may be a symptom of a Windows 95 MTU (Maximum Transmission Unit) problem. To find out which it is, compare the display of "Bytes received/sec." in System Monitor (see "Any Windows 95 tips?" to set that up) to the characters per second reported by your downloading application (e.g., FTP client or Web browser). These two values should be within about 10%; e.g., if your "Bytes received/sec." is 3,300 (typical of compressed data on a good 28800 connection), your characters per second should be about 3,000. If instead the characters per second is 1,000-1,600, you are getting a lot of wasted retransmissions that are probably due to the Windows 95 MTU problem.

The only reliable work-around that the author has found for this problem is to add the "MaxMTU" parameter to your Registry and set it to a value of 576. (MaxMTU and other networking parameters are documented in the free Windows 95 Resource Kit Help File.) There are two ways to accomplish this:

  1. Download and install TCPIPCFG, a Control Panel "applet" that makes it easy to adjust MaxMTU. (This applet will only run under Build 950 or 950a of Windows 95, not "OEM Service Release 2" or later versions. It will also not work on at least some non-English language versions of Windows 95; e.g., Catalan.)
  2. Follow the manual procedure.

Note: There are (unconfirmed) reports that MaxMTU does not work properly with SLIP, as opposed to PPP, connections. [new 10/18/96]

For those wishing to run tests, the author has found that (as of 10/5/96) this problem is reliably reproduced when downloading from <ftp://ftp.cygnus.com/pub/gnu-win32/> (the official FTP site for GNU-WIN32, the wonderful Win32 port of GNU tools for UNIX).

The Default Receive Window Fix and Hack [updated 10/5/96]

The following was contributed by Eric Gisin:

"Occasionally one sees slow downloads over dial-up PPP connections. I have never seen a plausible explanation for this in the comp.os.ms-windows.* newsgroups, but did find an explanation in one of the UNIX newsgroups.

"Apparently Solaris 2.3/2.4/2.5 have a TCP/IP bug that causes every packet to be sent twice when the network delay exceeds some threshold. You will observe the modem receiving data most of the time, but the transfer rate will be half of what it should be (1.6KB/s for 14.4, 3.2KB/s for 28.8).

"You can work around this bug both on the server and in Windows 95. If your provider's Sun server has this problem, make them fix it! [See 'Initialize the ReTransmit interval']

"In Windows the work-around is to reduce the Default Receive Window from its default of 8192, thereby reducing the network delay. I haven't verified this myself, as I rarely see the problem. If you can verify this solution, let me know and I will get it into an FAQ.

"If you aren't using TCP/IP on a LAN, you can set Receive Window to 4096 with no drop in performance and an improvement in interactive response (while downloading) of one or two seconds. Reducing the size of the Default Receive Windows probably is probably a general fix for many "mysterious" bugs, including the Solaris bug.

"Here is a registry hack that makes changing TCP/IP parameters easy. Maybe Microsoft could incorporate these changes into nettrans.inf.

[Note: No benefit was observed from the Default Receive Window Fix in extensive testing by the author of this FAQ, and the Hack appears to produce results inconsistent with Microsoft documentation on Default Receive Window. It is therefore presented here only in the hope that it might help those for whom MaxMTU might not work.]

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What is Distinctive Ring? [new 4/11/96]

How can I use a single phone for fax/data/voice? [new 9/20/96]

There are basically four methods of sharing an incoming phone line (without resorting to custom programming):

  1. Install a "Call Router" device on your regular phone line. (The cost is in the range of $50-300, depending on features. Sources on the Internet include Black Box, Hello Direct, and Sparco Communications.) You plug your modem, fax machine, answering machine, and/or voice telephone into the device. The device answers incoming calls, and directs them to the appropriate connected unit. Some devices do this with a series of voice prompts that instruct the caller to press different phone buttons for different services. Others do it by listening to the incoming call, and making a selection (guess) based on what they "hear." Drawbacks to this method are that voice prompting can confuse calling modems, and that your computer would need a second modem to receive both fax and data calls.
  2. "Silent Answer." This is a fax modem feature in certain Diamond/Supra modems that allows a fax modem to share a voice line. The modem answers, but does not use the normal fax answer tones. Instead it listens for tones from a calling fax. If it hears such tones, it automatically picks up the call and goes into fax mode, possibly cutting off an answering machine. Otherwise, it does not disturb the call. The drawback to this method is that it does not support data calls.
  3. Obtain "Distinctive Ring" service, and use a modem and software that support it. This service, offered by some (but not all) local telephone companies, gives you more than one phone number for a single phone line. Each number has a "distinctive" ringing pattern that can be detected by attached equipment. An attached fax/modem and software that support Distinctive Ring can then tell whether a call is coming in on the fax, data, or voice number, and handle the call in the appropriate manner. (Distinctive Ring can also be used with certain kinds of Call Routers. See above.) Distinctive Ring is usually not free, but less expensive than multiple phone lines. The drawbacks to this method are the monthly charge, and the possibility that the service may not be available in your area.
  4. Use a modem and software that support incoming Call Discrimination (also called "Adaptive Answer" or "Call Select"). Certain fax/data modems can discriminate between fax and data calls; certain so-called "voice" modems can discriminate between fax, data, and voice calls. The modem answers the call, and uses a combination of listening and trying (tones) to determine (guess) the type of incoming call. A voice modem and appropriate software can also employ voice prompting like certain Call Routers (see above). The modem then notifies the software of the type of call. The software is expected to take the appropriate action. Some modems do a better job of Call Discrimination than others.

The personal preference of the author is Call Discrimination. The problem is that good software that supports Call Discrimination has been hard to find. Although Version 2.xx of Procomm Plus for Windows has such support, it does not work well with all modems (see "Does USR Adaptive Answer work with Procomm Plus for Windows?"), and the author does not otherwise recommend the program (see "What are the best [data/fax] comm programs for Windows?"). Microsoft TAPI promised to address this need, but TAPI has been slow in coming. (See "What is TAPI?") Symantec WinFax PRO 7.0, also available as part of the Symantec CommSuite 95, finally delivers on that promise. Here's how to make Call Discrimination work on the USR Sportster 28800 Vi in Windows 95 with fax and the Dial-Up Networking Server (Microsoft Plus!):

Having done all this, the author's Windows 95 system, even with just the Symantec CommBar running, will answer calls on a Sportster 28800 Vi (internal), and connect them to either WinFax or the Windows 95 Dial-Up Networking Server as appropriate. It's also possible for the author to retrieve faxes remotely. (When connected to the Dial-Up Networking Server from a remote location, it's even possible for the author to access UNIX hosts running Samba that are connected to the Windows 95 PC over an Ethernet TCP/IP network.) All in all, it's an impressive display of technology. The one catch is that certain failure modes will cause WinFax to go out of fax auto-answer mode, even though the option is still checked; if and when this happens, open Setup | Receive and click OK.

If for data you need "mini-BBS" capability instead of networking, you can substitute the Host Mode in Symantec WinComm PRO 7.0, also included in the Symantec CommSuite 95, although this has not been tested by the author. The principal drawback is that WinComm PRO 7.0 currently suffers from bugs and other problems, including excessive CPU usage in Host Mode. Or you can try some other TAPI-complaint application (e.g., remote access software), but be warned that this is still new territory, and that you may have difficulty getting everything to work together properly.

Symantec TalkWorks, also included in the Symantec CommSuite 95, adds voice support, but has not been tested by the author.

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What is Caller ID? [new 4/11/96]

Caller ID is a technology that makes it possible for the called party to see the telephone number of the caller on a special device while the incoming call is ringing. It is also possible for a modem with Caller ID capability to obtain the telephone number data and report it to special software, which can use the data for purposes like security validation, event logging, and/or data access (e.g., of a caller's credit history). Caller ID is an optional service that is being offered by more and more local telephone companies now that the FCC has mandated nationwide deployment. (See "Caller ID to be available nationwide")

Caller ID has obvious applications in telephone mail-order, emergency services, dial-in communications, and for those that simply want to screen their calls. However, it can also invade the privacy of a caller, disclosing information that the caller would prefer not to disclose. (Your telephone number is a key that could be used to instantly access the vast amount of information about you that has undoubtedly been compiled in public and private databases without your knowledge or consent.) Caller ID can be blocked on a per-call or a per-line basis. Check with your local telephone company.

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How do I shut off Call Waiting? [new 4/11/96]

Why won't Call Waiting interrupt my modem connection? [new 10/16/96]

Call Waiting is a phone service option that allows you to be interrupted by an incoming call while you are using the phone line. If you are using the phone line for data or fax, the "beep" that signals the incoming call can cause an abrupt disconnection, which can be a problem.

To temporarily disable Call Waiting for a single outgoing call, there is often a special code that can be dialed before the phone number. With tone dialing service, this special code is usually "*70" (e.g., instead of dialing say "555-1212", you would dial "*70,555-1212", with the comma being used to signal your modem to insert a brief pause between the special code and the phone number); with pulse dialing service, this special code may be "1170". Check with your local phone company to be sure. Better comm programs have an option to insert the special code automatically.

On the other hand, you may actually want Call Waiting to interrupt a data or fax call, so that you do not miss an important incoming call. However, V.34 modems are designed to overcome "line noise" like Call Waiting, and they may not be disconnected by the "beep." Other than getting another phone line, there may be no possible work-around.

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How do I keep my data/fax call from being interrupted? [new 4/11/96]

It goes like this. You have a single line with multiple extensions that you use for both voice and fax/data. You are on-line in the middle of a large file transfer. Someone else picks an extension in another room, and bang, your connection is lost sending the file transfer down the drain.

There is an easy way to prevent this problem. Obtain a "Line Protector" for each extension phone. When your modem is on-line, the Line Protector will automatically prevent the attached phone from interrupting your connection. A Line Protector is inexpensive, and readily available on the Internet (e.g., Black Box or Hello Direct) or from Radio Shack (which calls it a "TeleProtector"). Some "Call Routers" will also provide this kind of protection. (See "How can I use a single phone for fax/data/voice?")

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How can I make fax work better? [revised 12/30/96]

There are three popular standards for fax modem commands (used by fax software applications):

Class 1
A low-level standard, Class 1 puts the most burden on your fax software and your host CPU, but also gives the most control. Slower systems may have problems sending and receiving faxes in the background with Class 1.
Class 2
A de facto standard promulgated by Rockwell, so-called Class 2 is widely supported by fax software, and takes much of the low-level load off of your system, which can improve faxing in the background, particularly if you have a slower system.
Class 2.0
A true standard for higher-level fax commands, Class 2.0 is notably supported by USRobotics, but is not widely supported in software as of this writing. It is not compatible with Class 2, although it can provide similar benefits.

Consumer-grade fax modems have a number of weaknesses and deficiencies, not all of which can be completely overcome. That noted, here are some suggestions for making your fax work better:

High-end fax modem products have significantly better fax machine coverage, reliability, and performance than consumer-grade fax modems. Such products are made by:

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Does USR Adaptive Answer work with Procomm Plus for Windows?

How to get Adaptive Answer to work on USR Sportster modems with Procomm Plus for Windows 2.xx (PW2.xx):

Adaptive Answer (called Call Selection by USR) works in Class 1 as well as Class 2.0 mode with 28.8 versions of both the USR Courier and Sportster. PW2.xx does not support Class 2.0 (only Class 1 and so-called Class 2), so it must be configured for Class 1 fax with USR modems.

The USR Adaptive Answer problem is that Datastorm apparently assumed that all modems are like Rockwell clones, which can enable Adaptive Answer while still in data mode. That doesn't work with USR modems, which require the modem to be in fax mode to enable Adaptive Answer.

Hopefully this problem will be fixed in a maintenance release. In the meantime the author's workaround to this problem is to put the USR Sportster modem into fax mode before enabling Adaptive Answer. (Apparently this method does not work on the Courier.) On the Setup | Fax Connection screen you will need to set:

Fax class: Class 1
Maximum transmit rate: 9600 [for reliability]
Maximum receive rate: 9600 [for reliability]
Class 1 adaptive answer command: +FCLASS=1+FAA=1 [no AT or ^M]
Adaptive answer connect message: FAX

Now you should be able to Setup | Auto Answer | Data and Fax. The command won't take when done online, but don't worry, just wait for PW2.xx to time out, and then Online | Initialize Data Modem to get everything working. Startup Host Mode, and you should be in business. Note: If you leave Auto Answer set to Data and Fax and put PW2.xx with HOST.WAX as an argument in your Startup group, PW2.xx will launch and initialize correctly for Adaptive Answer when you startup Windows.

Be sure to turn off Auto Answer before trying to make a data call out, or the call will fail since the modem will be in fax mode. Just Setup | Auto Answer | Off, and then Online | Initialize Data Modem.

A little bit of a kludge, but it does work on the Sportster.

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Any other USRobotics tips? [updated 10/27/96]

Warning: USR has indiscriminately slapped the "Sportster" name on so many different products that the author no longer feels it is a reliable product guide. For example, recent "Sportster 28800" and "Sportster 33600" modems have considerably different S-register settings as compared to the original "Sportster 28800" product. This invalidates a good deal of advice, including some of the material in this FAQ.

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Any other Windows 3.x tips?

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What are "voice" modems?

So-called voice modems fall into one (or sometimes more) of three categories:

  1. Modems that can function as an answering machine or voice-mail system. Some can also function as a speakerphone.
  2. Modems that can transmit data or voice over the same connection. (Radish "VoiceView")
  3. Modems that can transmit data and voice simultaneously over the same connection. (DSVD) Note that when voice is active, the speed of data transmission drops substantially.

Modems in the category 1 have been on the market for some time. Modems in categories 2 and 3 are just coming onto the market -- expect a continuing stream of new product announcements.

Note: None of these (current) voice modems permit you to:

See "Modems: the make-it-happen machines for the ultimately wired of the 90's"

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What is ISDN? [updated 10/11/96]

Probably the most likely successor to V.34, ISDN (Integrated Services Digital Network) provides up to 2-4 times the speed of V.34 over a standard local telephone line by using digital, rather than analog, signals. Years in the making, ISDN is finally being widely deployed in the U.S. at the time of this writing. To use ISDN you will need special, expensive equipment. A problem is that ISDN transmissions are typically not compressed; as a result, with compressible data the speed of a V.34 modem is often comparable to a single ISDN channel. In the opinion of the author, V.34 will probably be a cost-effective alternative to ISDN for years to come.

Although ISDN is a digital transmission medium, there are some ISDN products that will also allow you to connect to conventional analog modems (e.g., USR Courier I-modem with ISDN/V.34, ZyXEL Elite 2864I, and ZyXEL Prestige 2864I).

Microsoft has released an updated "ISDN Accelerator Pack" for Windows 95, which enables Windows 95 to make Dial-up Network connections over ISDN lines. [updated 10/11/96]

ISDN information is available at:

Magazine Reviews [new 8/30/96]

See also:

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What are "cable modems?" [updated 8/30/96]

So-called "cable modems" are devices which provide computer connectivity to and through a cable TV system. Despite a lot of hype, the technology is still experimental and the prospects are uncertain. One of several major problem is that many cable systems are not able to handle large incoming, as opposed to the more normal outgoing, bandwidth. Contact your local cable TV company for more information. See also:

Other "cable modem" resources on the Internet. (Note: This author cannot vouch for the accuracy of these resources.)

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What are ADSL, SDSL, and HDSL? [updated 8/30/96]

ADSL (asymmetric-digital-subscriber-line), SDSL (symmetric-digital-subscriber-line), and HDSL (high-bit-rate, digital subscriber line) are new telco technologies that have the potential to blow ISDN away. See:

Other ADSL, SDSL, and HDSL resources on the Internet. (Note: This author cannot vouch for the accuracy of these resources.)

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Any Windows 95 tips? What is TAPI? What is Plug and Play? [updated 10/11/96]

Connecting to the Internet [new 6/13/96]
An excellent resource is Microsoft's "Connecting to the Internet with Windows 95 Dial-Up Networking."
Connection Statistics [updated 10/11/96]
If you have a USR modem and want to access your ATI6 Link Diagnostics (see "Any other USRobotics tips?") for a dialup TCP/IP session, do the following:
1. You first have to "hack" the Registry:
(a) Run "REGEDIT" to launch the Registry Editor.
(b) Find the entry for your modem, which should be something like:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\Modem\0000
(If you have more than one modem, the number may be 0001, 0002, etc.)
(c) Change the "Reset" value, which will probably be "ATZ<cr>" or "ATZ4<cr>", to "AT&FE1Q0V1S0=0&C1&D2+FCLASS=0<cr>" or "AT&F1E1Q0V1S0=0&C1&D2+FCLASS=0<cr>" respectively.
(d) Restart Windows 95.
2. After disconnecting from a dialup TCP/IP session:
(a) Open Control Panel | Modems, and click on Diagnostics. You should see the name of your modem next to the COM port that it is on.
(b) Select the appropriate COM port and click on More Info. Windows 95 will run all of the common In commands, and then display the results.
Note: This is a temporary change for diagnostic purposes -- it is not recommended for regular use.
Dial-Up Networking improvements [updated 10/18/96]
Microsoft has released Dial-Up Networking (DUN) improvements as part of Version 1.1 of the ISDN Accelerator Pack. (You can safely install the ISDN Accelerator Pack even if you don't have or use ISDN, and then delete the ISDN support [under Control Panel | Add/Remove Programs | Windows Setup | Communications] leaving the improvements behind.) Improvements include DUN Server (previously available only in Microsoft Plus!), optional automatic connection without confirmation, integrated scripting (and SLIP), and placement of the DUN icon on the Tray rather than the Task Bar. Once installed, the new DUN capabilities can be accessed through My Computer | Dial-Up Networking | Connections | Settings. (Unfortunately, the improvements do not include a fix for the serious DUN MTU problem. See "Why does my Internet connection run at half-speed?")
Dial-Up Networking Freeware/Shareware [new 4/11/96]
Dunce: Dial-Up Networking Connection Enhancement
Keep Going: skips the dial-up Connect dialog box.
RoboDUN: alternative to Microsoft scripting.
RASPlus: "Hands free" Internet connection.
RTVReco: automatically re-establish dropped connections.
Dial-Up Networking Server [updated 10/18/96]
Available either in Microsoft Plus! or Version 1.1 of the ISDN Accelerator Pack (see "Dial-Up Networking improvements" above).
Information on setting up a dial-up networking server and/or client is available in:
"How to Enable Dial-Up Networking Server Capabilities"
"How to Connect to a Remote Server"
"Troubleshooting Browsing with Client for Microsoft Networks"
"Microsoft Plus! Readme.txt File Contents (2 of 2)"
"Technical Guide to Windows 95 Remote Connectivity"
Other Microsoft (Knowledge Base) resources
Dial-Up SLIP and Scripting Support [updated 10/11/96]
Adds SLIP and scripting capabilities to the basic PPP support in Windows 95 Dial-Up Networking. Part of the Windows 95 on CD-ROM Extras, and also included (and better integrated, along with other Dial-Up Networking improvements) in Version 1.1 of the ISDN Accelerator Pack. (You can safely install the ISDN Accelerator Pack even if you don't have or use ISDN, and then delete the ISDN support [under Control Panel | Add/Remove Programs | Windows Setup | Communications] leaving the improvements behind.)
HyperTerminal PE
HyperTerminal Personal Edition, an upgrade to Windows 95 HyperTerminal that provides improvements (auto-redial on busy and ZMODEM Crash Recovery) as well as bug fixes, is available from Hilgraeve at no charge.
Installing your modem "driver" [new 7/27/96]
It is very important to use the correct and latest INF file for your modem -- "Standard modem" may well cause problems. To change or install a new INF file:
* Obtain the correct and latest INF file for your modem from the modem manufacturer (see "Modem Companies on the Internet"). Copy it to your \WINDOWS\INF directory (which is hidden, but definitely there).
* Delete the files DRVIDX.BIN and DRVDATA.BIN from your \WINDOWS\INF directory. (You do not need to back them up, because they will be recreated automatically.)
* Open Settings | Control Panel | Modems.
* Remove your modem.
* Restart Windows 95. During the restart, it should detect your modem automatically and install the driver. If it does, you're done; if not, continue…
* Open Settings | Control Panel | Modems.
* Click Add, and run through the automatic process. If it still does not find your modem, select if from the list of modems manually. Be sure that you know the manufacturer and correct, exact model of your modem.
Internet Explorer [updated 4/11/96]
Download the latest version of Microsoft's World Wide Web browser. Note: Installing Internet Explorer will give you auto-dial support for Windows 95 Dial-Up Networking with all 32-bit (but not 16-bit) Winsock applications. You can then uninstall Internet Explorer without losing auto-dial support if you prefer another browser (which you should reinstall after uninstalling Internet Explorer).
ISDN Accelerator Pack [updated 10/11/96]
Enables Windows 95 to make Dial-up Network connections over ISDN lines. The updated version also includes Dial-Up Networking enhancements (see above).
Kernel Update [new 4/24/96]
Solves WinSock memory leak problem. Not included in Service Pack 1 (below). Highly recommended. There have been a few reports of serious problems installing and/or running the kernel update, so be sure to back up your system before installing it (as you should with any system update).
Logs [updated 10/5/96]
Windows 95 can record log files that can be helpful in diagnosing problems:
* Modem Log: Settings | Control Panel | Modems | [select modem] | Properties | Connection | Advanced | Record a log file (look for the file as \WINDOWS\MODEMLOG.TXT). See "How to Create and Use the Modemlog.txt File."
* Dial-Up Network Log: Settings | Control Panel | Network | Dial-Up Adapter | Properties | Advanced | Record a Log File | Yes (look for the file as \WINDOWS\PPPLOG.TXT). See "How to Create a Ppplog.txt File."
Note: The logs do not keep growing indefinitely.
Microsoft AnswerStation [new 6/13/96]
Put your VoiceView modem (see "What are "voice" modems?") to work!
Modem Diagnostics
The best way to verify that your modem is working is to open Control Panel | Modems, and click on Diagnostics. You should see the name of your modem next to the COM port that it is on. (If not, you need to reinstall your modem, as described above.) Select the appropriate COM port and click on More Info. Windows 95 will try all of the common In commands, and then display the results. The display will frequently include a description of the modem and the version of firmware it is running.
Modem Initialization [new 10/11/96]
To modify your modem initialization, go to Control Panel | Modems. Select your modem and then click Properties. Click Connection, then Advanced. Enter any extra settings in Extra Settings (without the "AT").
MTU [new 10/5/96]
Unless you explicitly set MaxMTU in the Registry, you may experience abnormally low file transfer speeds (half-speed or even less) with certain servers under Windows 95 Dial-Up Networking. See "Why does my Internet connection run at half-speed?"
Plug and Play
Windows 95 supports "Plug and Play," a standard that makes it possible for the operating system to automatically detect and configure most peripheral devices. Plug and Play modems are available from USRobotics, Diamond/Supra, and other manufacturers.
Resource Kit [new 10/5/96]
The free Resource Kit Help File is an invaluable source of Windows 95 technical information, particularly on networking (including Dial-Up Networking).
Service Pack 1 [new 4/11/96]
Various fixes and improvements have been collected by Microsoft into the first Service Pack. Highly recommended.
Support [new 6/13/96]
Microsoft support on the Internet.
Symantec CommSuite 95 [new 3/1/96]
While providing a rich feature set, this product, including WinFax PRO 7.0 and WinComm PRO 7.0, suffered in its first release from excessive memory requirements, poor performance (even on fast systems), modem compatibility problems (particularly with USRobotics modems), and bugs. The WinFax 7.0 Maintenance Updates correct many (although not all) of those problems -- be sure to get them.
System Monitor [updated 10/5/96]
The System Monitor accessory that comes with Windows 95 has a wealth of hidden features, among them the ability to display modem throughput in real time. To get it working:
* Open Control Panel | Modems; select your modem; click Properties | Connection | Advanced; check "Record a log file"; and then click OK to close all the dialogs.
* Make a connection with your modem using 32-bit software (e.g., HyperTerminal, which comes with Windows 95).
* Start System Monitor; choose Edit | Add Item. You should see your modem under Category. Select your modem, then under Item select "Bytes received/sec." and/or "Bytes sent/sec.", and click OK.
If you have problems, see "System Monitor Does Not Display Modem Statistics."
TAPI
TAPI (Telephony Application Programming Interface) is an architecture being developed by Microsoft to bring order out of the past chaos in comm software and modem interaction. "TAPI compliant" applications rely on new standard Windows services (provided by the Unimodem driver/provider) rather than controlling the modem directly, which makes it possible for multiple comm applications to share the same modem. With a proper modem INF file and a sufficiently capable modem, separate data, fax, and voice applications could be "registered" with TAPI (once Microsoft's implementation is complete) such that an incoming call is automatically connected to the right application. (See "How can I use a single phone for fax/data/voice?") TAPI is being developed first for Windows 95, with Windows NT to follow. TAPI resources for developers are available on the Internet. [updated 4/24/96]
Telephony Location Selector [new 4/11/96]
For mobile users, provides an easy way to change your location for telephony applications (e.g., Windows 95 Dial-Up Networking). Part of the Microsoft Power Toys.
Unimodem V
"Unimodem V is Microsoft's newest release of Unimodem, the Windows universal modem driver/telephony service provider for data/fax modems. Unimodem V provides the driver support that sits between telephony applications and voice modems and allows them to work together. This driver adds the most-requested features to support data/fax/voice modems, including wave playback and record to/from the phone line, wave playback and record to/from the handset, and support for speakerphone, Caller ID, distinctive ringing, and call forwarding." [Quote from Microsoft] Unimodem is TAPI-complaint. At initial release, Unimodem V supports the following modems:
Aztech Systems
Cirrus Logic
Compaq Presario models 520, 720, 820, and 920
Compaq Presario wave driver and wrapper
Creative Labs Phone Blaster
Diamond Multimedia TeleCommander 2500
Logicode 14.4 data/fax/voice PCMCIA
Rockwell PCMCIA reference design
Updated Drivers [updated 4/9/96]
Audio
CD-ROM
Display
IrDA (Infrared Driver)
ISDN Accelerator Pack
Modem (Microsoft)
Mouse
Network
Other
Pointer
Printers
Storage
Unimodem V
UPS

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Any other sources of related information? [updated 6/6/96]

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Where can I get more help? [new 5/20/96]

Newsgroups can be excellent resources. You can often find answers to questions you didn't even know you had. If you don't find what you are looking for, you can post your own questions, and usually get answers within a day or two, sometimes within hours. Just remember that a good deal of nonsense also gets posted to Usenet.

NOTE: It is very important to "learn the ropes" before posting to newsgroups. Resources to help you do this include:

The modem-related newsgroup resources include:

Usenet

comp.dcom.fax
Unmoderated discussion of fax modem-related issues (not conventional fax machines).
comp.dcom.isdn
Unmoderated discussion of ISDN. (See "What is ISDN?")
comp.dcom.modems
Unmoderated discussion of data modem-related issues.
comp.os.ms-windows.apps.comm
Unmoderated discussion of Microsoft Windows communications applications
comp.os.os2.comm
Unmoderated discussion of IBM OS/2 communications-related issues
comp.sys.mac.comm
Unmoderated discussion of Apple Macintosh communications-related issues
comp.sys.ibm.pc.hardware.comm
Unmoderated discussion of communications hardware (e.g., serial ports) for PC-compatible computers

Microsoft

microsoft.public.win95.commtelephony
Unmoderated discussion of communications over telephone lines (e.g., data/fax/voice modems, ISDN) under Windows 95
microsoft.public.win95.dialupnetworking
Unmoderated discussion of Dial-Up Networking (DUN) under Windows 95

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How can I connect my modem to a digital phone system?

Your modem won't work on the kind of digital phone that you typically find in businesses and hotel rooms, and it can be hard to find a standard phone jack when you need one. There are a number of devices on the market to solve the problem. Typically you have to disconnect the handset from a digital phone, plug the handset into the device, and then plug the device into the handset jack on the phone. Then you connect your modem to the device with a standard phone cord.

The author gives a qualified recommendation to the Konexx Konnector Model 111. The product can be powered by a 9v battery or from an AC power adapter, both of which are included. The biggest weakness of the Konnector Model 111 is that, like other similar products, you have to experiment with a non-intuitive 4-position switch.

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What modem initialization string should I use? [updated 11/8/96]

  1. The best resource for modem initialization strings is the documentation that came with your modem, or other information provided by your modem manufacturer.
  2. Windows 95 comes with INFormation files that provide proper initialization for many popular modems. (It is very important to use the correct and latest INF file for your modem -- "Standard modem" may well cause problems. See "Installing your modem 'driver'" under "Any Windows 95 tips?") [new 11/8/96]
  3. Many comm apps are another good resource, because they come with recommended modem initialization strings.
  4. An online resource is Ask Mr. Modem. Note: This author cannot vouch for the accuracy of Ask Mr. Modem. [updated 11/8/96]

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Where can I get information on my Rockwell-based modem? [updated 4/11/96]

The best source for information is of course the modem manufacturer.
Generic information is available from Rockwell International.

"RPI" (Rockwell Protocol Interface)

The author advises against the purchase of any RPI modem. RPI uses your system processor, rather than a processor in the modem, to implement protocols. This requires special software support, which may well not be available for your favorite comm app.

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What about magazine reviews? [updated 8/30/96]

Take magazine modem reviews with a grain of salt -- few if any magazines perform the kind of thorough interoperability and real-world tests that are needed to properly compare modems.

Note that the apparently diverse computer magazine publishing field is actually dominated by a relatively small number of publishers, particularly Ziff Davis. Reviews from different magazines owned by the same publisher tend to have a shared editorial bias, if for no other reason than that testing is often done by a shared facility (e.g., ZD Labs). The publisher is noted in parentheses.

Analog Modems:

ISDN: [new 8/30/96]

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Which 28800 modem should I buy? [updated 9/07/96]

(For other hardware recommendations, see "Hardware Recommended by John Navas") [new 9/07/96]

In the opinion of the author, 28800 modems are still too immature to shop on price alone because there are still performance and interoperability problems. (To avoid interoperability problems you may want to purchase the same brand as the modem you will be most frequently calling.)

Take magazine modem reviews with a grain of salt -- few if any magazines perform the kind of thorough interoperability and real-world tests that are needed to properly compare modems. (See "What about magazine reviews?")

Furthermore, like software, modem preferences are a highly personal matter -- a terrific modem for one person may be a dog for another person, and vice versa. That noted, the personal assessment of the author is as follows:

Medium-High End

USRobotics Courier V.Everything
In the opinion of the author, this is quite simply the best reasonably-priced modem available. It's a particularly good choice if you have poor phone lines, if you have to make difficult connections, or if you have to connect to a wide range of modems. A strength that the Courier shares with the Sportster is that its DSP code is stored with its firmware (in Flash in the Courier, ROM in the Sportster), so that it can be easily updated (unlike most modems, which have fixed "datapumps"). A firmware update (7/5/95 or later for USA modems) that supports Selective Reject and draft V.34 speeds up to 33.6 Kbps is now available. The Courier is a good choice for a small BBS, and USR has an attractive SYSOP program. Otherwise the best way to get a good deal may be to find a cheap used 9600 bps or above Courier and take advantage of the USR upgrade program.
Motorola [updated 6/13/96]
An excellent company with ISO 9001 registration and a reputation for excellent products. Not evaluated by the author:
* 326XFAST: V.34 modems designed for networking.
* V.3400: A reputation as an excellent, if pricey, modem. Does not support V.FC.
* V.34R: Similar to the V.3400, but without the LCD display.
* Premier 33.6: Positioned to compete with the USR Courier. Firmware in Flash. Claimed maximum compression is 8:1. Does not support V.FC and only supports Class 1 fax.
Microcom
A reputation for very good modems. Not evaluated by the author.
Bay Networks/Penril
A reputation for excellent, if pricey, modems. Not evaluated by the author.
Telebit
A reputation for excellent, if pricey, modems. Not evaluated by the author. Does not support V.FC.
Zyxel
The Elite 2864 is feature rich (although it does not support V.FC), Flash upgradable, and has the added advantage of being user-upgradable to ISDN (Elite 2864I). However, in the author's tests it does not yet measure up to other modems in connection speed and reliability.
AT&T Paradyne
A reputation for excellent, if pricey, modems. Not evaluated by the author. Does not support V.FC. Supports a proprietary V.34 extension for speeds up to 33.6 Kbps. (Note: Paradyne is reportedly up for sale, so its future is uncertain -- see "AT&T Seeks Buyer For Paradyne" and "PC Magazine Newswatch for Thursday, October 19, 1995")

Consumer Grade

Motorola [updated 6/13/96]
An excellent company with ISO 9001 registration and a reputation for excellent products. Reports on the PowerClass and Lifestyle modems (distinguished from each other only by features) are mostly positive. However, there have been reports of a few problems (e.g., Motorola's Customer Note of July 27, 1995, which Motorola is to be commended for publishing). Limitations include a maximum speed of 28.8 Kbps, no V.FC, and no Class 2 or 2.0 fax.
Newer models include:
* VoiceSURFR: V.34 28.8 internal modem with data, fax (Classes 1 & 2), voice and full-duplex speakerphone.
* ModemSURFR: V.34 28.8 internal/external modem with data and fax (Classes 1 & 2).
* OnlineSURFR: ModemSURFR with bundled Internet software.
USRobotics Sportster 28800/33600 [updated 4/27/96]
The popularly-priced Sportster 28800/33600 is a very good modem. (See "SHOOTOUT: Sportster vs. Courier") A strength of the Sportster is that it supports several optional V.34 features (notably split speed) that are not supported by some other popularly-priced modems. Be sure to get firmware dated 4/18/95 or later for USA modems; if necessary, call USR (847/982-5151) to get an upgrade. Certain 28800 Sportster models can be inexpensively upgraded to 33600 (including Selective Reject).
* The "Vi" model includes voicemail capabilities. It is otherwise the same as the standard model.
* The "Voice" model includes voicemail and speakerphone capabilities. It is otherwise the same as the standard model.
* The "DSVD" model includes Flash (like the Courier V.Everything) and DSVD (simultaneous voice and data over the same connection) capabilities.
* Warning: The Sportster "WinModem" is a proprietary design that requires special USR drivers that work only under Microsoft Windows. Make sure that you are willing to live with the attendant risks and inherent limitations before purchasing any proprietary product. [new 3/29/96]
*
Warning: The Sportster Si is essentially a Rockwell "Glue 'n Go" clone (see below); worse, it uses software (RPI) rather than hardware protocols. The author advises against the purchase of any RPI modem. (See Where can I get information on my Rockwell-based modem?)
* Warning: USR has indiscriminately slapped the "Sportster" name on so many different products that the author no longer feels it is a reliable product guide. For example, recent "Sportster 28800" modems have considerably different S-register settings as compared to the original "Sportster 28800" product. This invalidates a good deal of advice, including some of the material in this FAQ.
Diamond/Supra [updated 6/6/96]
In the opinion of the author, Diamond/Supra is the probably the best bet among the Rockwell chipset-based modems, particularly now that it has released firmware that supports split speeds. All 28800 Diamond/Supra modems can be upgraded to 33600.
Multi-Tech
Although high-end Multi-Tech modems have a good reputation, the author cannot recommend the popularly-priced MT2834ZDX. In the author's head-to-head real-world tests against the USR Sportster 28800, the MT2834ZDX was consistently one step slower, worse on difficult connections; in addition, operational idiosyncrasies caused problems with certain comm apps (e.g., HyperACCESS for Windows).
Hayes
Although Hayes has made excellent modems in the past, of late it has been slipping, and its 28800 products have exhibited interoperability problems. Because Hayes (inc. PPI) has now emerged from Chapter 11 (Bankruptcy) protection, the author no longer recommends against the purchase of Hayes products, but still advises caution for at least the next few months.
Practical Peripherals Inc. (PPI)
PPI is owned by and has been folded into Hayes. The same general comments apply.
Zyxel
The Omni 288S is the consumer grade version of the Elite 2864. Not evaluated by the author.
AT&T
AT&T has bailed out of consumer modems. Although good liquidation deals may be found, support could be a problem. Also be warned that there were two completely different AT&T consumer modem lines with similar names. The Dataport was based on AT&T's own modem technology; the low-cost Dataport Express was essentially a Rockwell "Glue 'n Go" clone (see below).
"Glue 'n Go" clones
In the opinion of the author, companies that simply slap a modem chipset on a board are currently a poor bet given the immaturity of 28800 products. (The author puts Best Data, Boca, GVC, and Zoom in this category.) Some do not support optional V.34 features such as split speeds.

Other modem companies on the Internet include:

Whatever modem you decide to purchase, the author strongly recommends that you get a return privilege from the dealer (in case you run into problems).

Note: No consumer grade modem should be used for a large BBS or an Internet service provider. In the long run the savings in maintenance and support costs with rack mount modems more than offsets their higher initial purchase price. The author recommends the USRobotics Total Control system.

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Where can I get a good deal on a modem?

In the opinion of the author, 28800 modems are still too immature to shop on price alone. If you run into (all too common) performance or interoperability problems, the best way to deal with them may be to return the modem and try a different brand, which may not be possible with a low price source.

The author recommends WH Networks Communications.

Other sources on the Internet include:

One of the best mail-order sources is Computability (800/554-9950 or 414/357-8181).

Please note that the author has no connection to any of the sources listed here.

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Trademarks belong to their owners.