NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/dcom/modems-part2/11827

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Path: news.aimnet.com!news
From: [e-mail] (John Navas)
Newsgroups: comp.dcom.modems
Subject: The Navas 28800 Modem FAQ - 3/6
Date: Sun, 21 Apr 1996 17:27:58 GMT
Organization: The Navas Group of Dublin, CA, USA
Message-ID: <[e-mail]>
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<<cont>>

Why do connections sometimes seem to run slower and slower?



    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'?[310]") 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?[311], Any Trumpet Winsock tips?[312], and Why can't I get back
   on-line after I escape to command mode?[313])

    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

    USR now has a fix for this problem:

        "Dear USRobotics Customers:



        USR has received many comments about a condition identified by s
     ome users as Spiraling Death Syndrome. The conditions stated are tha
     t the Sportster v.34 modem degrades it's throughput speed as the pro
     duct heats up.



        Although we have been unable to duplicate the problem on a large
      scale, we have duplicated these symptoms on a very intermittent bas
     is. However, the current release of v.34 code (dated 4/18/95) has al
     lowed for greater variances in ambient temperature swings in additio
     n to greater compatibility to non-USR products. As a result, for the
      next 30 days, USR is offering a code upgrade and fulfillment progra
     m at no cost to our customers. Until June 9, 1995 customers simply n
     eed to contact USR at 708-982-5151 and prompt for Technical Support
     to validate the symptoms. Upon validation, USR's Customer Service De
     partment will process the replacement code order.



        Please note that this is a limited time offer. Effective Monday,
      June 12, 1995 the standard code upgrade program goes back into effe
     ct. This program requires a $15 fee to cover the extraction tool, ha
     ndling & shipping.



        We thank our customers for continued support of USRobotics produc
     ts and it is our wish to maintain customer support and loyalty."



    The author urges all Sportster 28800 owners to take advantage of this
   offer. Even though the original offer has expired, you may still be able to
   get a free upgrade if you (politely) insist on it. Or you can purchase the
   low-cost upgrade to 33600, which contains all previous improvements, if you
   have one of the Sportster models for which the upgrade is available.

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



      If possible try a different modem to see if the problems persist or
      not.

      Try to improve your connection -- the Sportster 28800 may be falling
      back in response to noise bursts on the line. (See "Why don't I get
      28800 bps speed on my connections?[314]")

      If you have the external Sportster 28800, try turning the volume control
      all the way down before the initial negotiation.

      You can disable fallback on the transmit side (the receive side is not
      affected) by setting the undocumented option of S15=2. The downside is
      that you may get disconnected if line conditions deteriorate enough to
      warrant a fall-back and/or you may experience more retraining. (This
      option is documented for the Courier V.34.)

      If you have 11/30/94 or later Sportster firmware (date for USA modems),
      you can lock the transmit speed (but not the receive speed) in a range
      with &Nn&Un (e.g., &N14&U12 locks the transmit speed between 28800 and
      24000). With an appropriate range, this may be more reliable than S15=2.
      (However, it does not work on the Courier.)



    Button[315] [Return to top[316]]
   ___________________________________


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



How can I use a single phone for fax/data/voice? [new 4/11/96]



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



      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[317], Hello Direct[318], and Sparco
      Communications[319].) 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.

      "Silent Answer[320]." This is a fax modem feature in certain Supra[321]
      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.

      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.

      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[322] 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?[323]"), and the author does not otherwise
   recommend the program (see "What are the best [data/fax] comm programs for
   Windows?[324]"). Microsoft TAPI[325] promised to address this need, but
   TAPI has been slow in coming. (See "What is TAPI?[326]") Delrina[327]
   WinFax PRO 7.0, also available as part of the Delrina 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:



      Make sure that you have current modem firmware.

      Install the latest INF file for the Vi[328] from the USR BBS/FTP
      server.

      Install the Unimodem V[329] driver from Microsoft.

      You must also have the latest WinFax 7.0 Maintenance Update[330].

      Use Control Panel | Modems to first Remove your modem, and then Add it
      back using the proper INF file entry.

      Configure your modem in WinFax Setup | Modem, and be sure to select
      TAPI.

      Use WinFax Setup | Receive to enable Call Discrimination. (You should
      not have to fool with the Registry settings.) Be sure to click OK even
      if you made no changes.

      Open Dial-Up Networking and select Connections | Dial-Up server to
      enable the Allow Caller Access option. Click Apply, and make sure that
      Status shows or switches to "Monitoring."

      It's also important to be sure that you have NetBEUI installed for your
      Dial-Up Adapter (under Control Panel | Networking) -- TCP/IP will not do
      the job.

      And don't forget to set the Sharing option (in My Computer or Explorer)
      for drives and/or folders you want to be able to access.



    Having done all this, the author's Windows 95 system, even with just the
   Delrina CommBar running, will answer calls on a Sportster 28800 Vi
   (internal), and connect them to either WinFax or the Windows 95 Dial-Up
   Server as appropriate. It's also possible for the author to retrieve faxes
   remotely. (When connected to the Dial-Up server from a remote location,
   it's even possible for the author to access UNIX hosts running Samba[331]
   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 Delrina WinComm PRO 7.0, also included in the
   Delrina 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.

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

    Button[332] [Return to top[333]]
   ___________________________________


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[334] has mandated nationwide
   deployment. (See "Caller ID to be available nationwide[335]")

    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.

    Button[336] [Return to top[337]]
   ___________________________________


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



    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, some modems will not be disconnected by the "beep," and there may
   be no possible work-around.)

    Button[338] [Return to top[339]]
   ___________________________________


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[340] or Hello Direct[341]) 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?[342]")

    Button[343] [Return to top[344]]
   ___________________________________


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[345] 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.

    Button[346] [Return to top[347]]
   ___________________________________


Any other USRobotics tips?



    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.



      Certain 28800 Sportster models can be inexpensively upgraded to 33600
      (including Selective Reject[348]).

      Useful modem commands:

      ATI6, issued after a disconnect[349], will tell you the reason for the
      disconnect.

      ATI6 will tell you your current modem-to-modem connection speed if you
      escape (e.g., with "+++") to command mode while online. With
      split/asymmetric speeds (see What are split/asymmetric speeds?[350]),
      ATI6 will report the two speeds as receive/transmit. (See also "Why
      can't I get back on-line after I escape to command mode?[351]" To
      display the current connection speed when using Trumpet Winsock on a
      SLIP/PPP link, see "Any Trumpet Winsock tips?[352]")

      ATO will return you to on-line mode after you escape to command mode;
      ATO1 will also request a retrain[353] (which may help if line conditions
      have changed substantially).

      ATI7 will tell you what firmware version (date) you have.

      For a good description of the output of the ATI6 and ATI11 commands, see
      the FAQ by USR UK[354].

      If you experience problems connecting to certain V.34 modems:

      It may help to disable the 3429 symbol rate (S54.5=1), which confuses
      certain modems (e.g., Hayes) that are not fully V.34 compliant during
      negotiation.

      It may help to disable V.FC (S56.7=1).

      It may help to disable V.42 detect phase (S27=48).

      If you experience problems connecting to certain V.34/V.FC modems, or
      you otherwise want to connect with V.FC when the remote modem supports
      both V.34 and V.FC, disable V.8 (S54.7=1), which effectively disables
      V.34.

      If you have a particular number where you sometimes connect at a very
      slow speed but get a much higher speed when you immediately redial, find
      out if there is a Hayes modem at the other end. If so, it may be
      possible to correct the problem by updating the Hayes firmware.

      If you experience problems connecting to certain older MNP modems (esp.
      at 2400 bps), try S15=64. This option is only documented for the Courier
      ("Unusual MNP-Incompatibility"), but may work for the Sportster as
      well.

      If you hear a strange ringing sound after dialing and before the remote
      answers, that's Call Indicate. It's a good idea to disable it (S54.6=1),
      because it can cause connection problems with certain modems.

      Some users have reported that resetting the modem before each call
      improves the chances of a good connection. To do this, use ATZn instead
      of AT&Fn. The options for ATZn are:



        Z - reset and load profile Yn
        Z1 - reset and load profile 0
        Z2 - reset and load profile 1
        Z3 - reset and load &F0 defaults
        Z4 - reset and load &F1 defaults
        Z5 - reset and load &F2 defaults



        In other words, ATZ4 is a good alternative to AT&F1. Generally t
     he only problem is that you can't put more commands on the same line
      with ATZn as you can with AT&Fn; e.g., you can do AT&F1S11=55 but n
     ot ATZ4S11=55. If you have a comm program that can issue more than o
     ne initialization string (e.g., HyperACCESS for Windows or WinComm P
     RO), you can simply put additional commands in a second command stri
     ng; e.g., ATZ4 followed by ATS11=55.





      If you experience faxing problems, in addition to the other suggestions
      in this document (e.g., "What about third-party comm drivers for
      Windows?[355]" and "Any other Windows tips?[356]") you should make sure
      that you have firmware dated 4/18/95 or later. (For a firmware upgrade,
      call USR at 708-982-5151.) Otherwise, it might help to initialize the
      modem with S36=0. If you are using Delrina WinFax, you might also try
      limiting your send and receive speeds to 9600 bps by adding the
      following to the [General] section of your WINFAX.INI file:
       MaxTxSpeed=9600
       MaxRxSpeed=9600

      With the Sportster (not the Courier), watch out for which profile you
      have set. If Y1 is set (which selects profile 1 rather than profile 0),
      and you do (say) ATS11=55&W, and then later use ATZ to initialize your
      modem, you won't get the S11 setting you saved! The reason is that &W
      always saves to the profile 0, while ATZ loads whatever profile Yn is
      set to, in this case profile 1.

      Options that are controlled by dipswitches are not saved in NVRAM
      (profiles 0 and 1). If you want them to be in a known state without
      worrying about the dipswitches, you should set them in your
      initialization string (e.g., E1Q0V1S0=0&C1&D2 for the default settings).




    Button[357] [Return to top[358]]
   ___________________________________


Any other Windows 3.x tips?





      An upgrade to Windows for Workgroups 3.11 or Windows 95 is probably the
      best way to improve Windows communications.

      To improve transmit (upload) performance and/or fax reliability under
      Windows for Workgroups 3.11, put the following in the [386Enh] section
      of your SYSTEM.INI file:
       COMnTXFIFO=1
      where n is the number of your modem COM port (e.g., COM2TXFIFO=1). This
      enables use of the 16550 Transmit FIFO. (See "Do I need a 16550 UART?
      What is a UART?[359]")

      Be careful not to confuse Windows (standard) 3.11 with Windows for
      Workgroups 3.11 -- version numbers notwithstanding, they are not the
      same. Windows (standard) 3.11 is essentially Windows 3.1 with a few bug
      fixes (that do not directly affect modem communications), whereas
      Windows for Workgroups 3.11 has a considerably different internal
      architecture.

      If you get "Insufficient Memory to Run" errors when starting new
      applications when you still have sufficient Free Memory and System
      Resources (as displayed by Program Manager Help | About), one of your
      running applications is probably locking an excessive amount of memory
      below 1 Mb. (See "PRB: Avoiding 'Insufficient Memory to Run'
      Errors[360]") Utilities are available to deal with this problem:

      Memfix[361] (GNU "copyleft" license)

      MemPlus[362] (Shareware US$40)

      MoreMem[363] (Shareware US$40)

      If you experience lockups or strange behavior, try setting MaxBPs=400
      (or more) in the [386Enh] section of your SYSTEM.INI file.

      Contrary to "urban legends" it is possible to have a DOS application
      temporarily take over a COM port from a Windows application; i.e., it is
      possible to use a DOS program like DSZ[364] to handle ZMODEM file
      transfers for a Windows comm app with a less efficient ZMODEM
      implementation. The key to doing this is to set ComxAutoAssign=0, where
      x is the number of your modem COM port (e.g., Com1AutoAssign=0), in the
      [386Enh] section of your SYSTEM.INI file. (Because the exact details
      will vary from comm app to comm app, the rest of the exercise is left to
      the reader.)

      Updated Windows 3.x drivers[365] are available from Microsoft.

      Good general resources are Microsoft's:

      "Windows 3.1 and Serial Communications[366]" (also available as a
      downloadable file[367]).

      "Windows 3.1 Serial Communications Q & A Part 2[368]"

      The Windows Resource Kit[369] is also good, particularly the SYSTEM.INI
      section, which is viewable on the Web:

      Windows 3.1 Resource Kit SYSTEM.INI [386ENH] Section A-L[370]

      Windows 3.1 Resource Kit SYSTEM.INI [386ENH] Section M-Z[371]



    Button[372] [Return to top[373]]
   ___________________________________


What are "voice" modems?



  UNDER CONSTRUCTION -- PLEASE BE PATIENT.



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



      Modems that can function as an answering machine or voice-mail system.

      Modems that can transmit data or voice over the same connection. (Radish
      "VoiceView")

      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:



      Receive a voice call while your modem is in use. (For that you need a
      second phone line -- these modems cannot deal with Call Waiting.)

      Talk over the Internet. (For that you need a soundcard, and preferably
      one that is full-duplex, although this would be possible with a properly
      designed combo modem-soundcard product.)



    See "Modems: the make-it-happen machines for the ultimately wired of the
   90's[374]"

    Button[375] [Return to top[376]]
   ___________________________________


What is ISDN? [updated 4/9/96]



  UNDER CONSTRUCTION -- PLEASE BE PATIENT.



    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[377] and ZyXEL Elite
   2864I[378]).

    Microsoft has released the "ISDN Accelerator Pack[379]" for Windows 95,
   which enables Windows 95 to make Dial-up Network connections over ISDN
   lines. [new 4/9/96]

    ISDN information is available at:



      Ascend[380]:

      Pipeline 25[381]

      Pipeline 50 ISDN[382]

      Bellcore's National ISDN site[383]

      Best Data[384]

      Dan Kegel's ISDN Page[385]

      IBM[386]:

      WaveRunner[387] and WaveRunner PCMCIA[388] (see also "Mwave at
      Watson[389]")

      7845 ISDN NT-1 Extended[390]

      ISDN*tek Home Page[391] (ISDN products)

      Pacific Bell's ISDN User's Guide[392]

      PSI InterRamp[393] (large ISDN ISP)

      Motorola ISG[394]:

      BitSURFR[395]

      BitSURFR Pro[396]

      Racal-Datacom BRI 2000[397]

      Surf Communications[398] (ISDN access)

      3Com Impact ISDN Digital Modems and Adapters[399]

      Usenet comp.dcom.isdn[400]

      USRobotics[401]:

      Sportster ISDN 128K[402]

      Courier I-modem with ISDN/V.34[403]

      ZyXEL[404]:

      Elite 2864[405]

      Elite 2864I[406]



    See also:



      "Building The Data High Way[407]" (Byte)

      "Modems: the make-it-happen machines for the ultimately wired of the
      90's[408]" (Motorola)

      "Needed: A Digital Weatherman[409]" (PC Magazine)



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