Nebula 1994 June/NEBULA_SE.ISO/Documents/FAQ/Modems-faq/NetComm-faq

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From: [e-mail] (Anthony Rumble)
Subject: The NetComm Modem FAQ v1.1
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$revision: 1.1 $
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Date: Thu, 12 Aug 1993 01:08:40 GMT
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                          NetComm Australia
                          Frequently Asked
                           Questions List

                   Last Modified: August 11th, 1993

Archived at: The NetComm BBS (Numbers Below).

The FAQ is reposted bi-monthly onto :-
Usenet: news.answers,comp.answers,aus.comms,comp.dcom.modems
FidoNet: aust_modem, netcomm_support

Please mail any submissions/corrections to :-
                             : Internet [e-mail]
                             : FidoNet To:[e-mail] 3:712/400
                             : Compuserve NetComm,75300,3571
                             : NetComm BBS 02 888 6904

#NOTE: This FAQ only covers questions about the newer products.
       IE: Those after, and including, the SM7700 M7F.

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NetComm Tech. Support BBS/voice numbers:

NetComm Australia, Sydney
        BBS:   02 888 6904
               02 878 7412
        Voice: 02 805 1488
        FAX:   [phone]

NetComm Australia, Melbourne
        Voice: 03 696 2222
        FAX:   [phone]

NetComm Australia, Brisbane
        Voice: 07 852 1666
        FAX:   [phone]

NetComm Australia, Perth
        Voice: 09 470 5111
        FAX:   [phone]

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Questions :-

Q: Is there a HELP Screen/Function in the modem?
Q: How do I identify what modem I have?
Q: I used the #J command to connect to a LAPM modem and it didn't
   disable LAPM.
Q: I have an Amiga computer and every time I turn on Hardware flow control
   I suddenly can't talk to the modem anymore?
Q: I can't connect to some modems in LAPM/MNP Auto-Reliable (\N3) mode
   even though these modems have MNP?
Q: What is flow control?
Q: What is the S register 33 all about?
Q: What are the Error Correction connect/fallback timings in the Series 4
   SmartModem?
Q: What is MNP10?
Q: I sometimes connect with MNP4/v.42bis on to some non v.42bis modems?
Q: What do I do if I think my modem is faulty?

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Q: Is there a HELP Screen/Function in the modem?

A: Yes there is. You can access the general HELP screen by typing
   in command mode AT? <return>

   This will give you a list of all the modem commands and a short
   description of each command.

   In some of the later Series 4 releases, you can search through the
   help text by doing this :-

   AT?search string

   ie/ AT?S33

   Will bring up the help text for the S register 33.

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Q: How do I identify what modem I have?

A: There are 3 ways of identifying what modem you have.
   1:   Which is by far the most accurate, is to execute the command 'ATI9'
        within a Terminal Program. This will return the Manufacturers
        id string.

        For the Current Series 3 E7 it will look like this.
        SmartModem V.32bis E7  vx.xx T6 0xxx (C) NetComm 1991

        For the Current Series 3 M7F it will look like this.
        SmartModem V.32bis M7F vx.xx T7 0xxx (C) NetComm 1991
                                        ^^^^
                                        This is the firmware revision

        For the Current Series 4 E7 it will look like this.
        Series 4  V.32bis Modem Y5D vX.XX (C) NetComm (Aust) 1992

        For the Current Series 4 M7F it will look like this.
        Series 4  V.32bis Modem Y7D vX.XX (C) NetComm (Aust) 1992

        The 2400 bps products will be virtually the same, except a 4
        instead of a 7.

   2:   Another Method is by looking on the front panel.
        A Series 3 will have this on the front panel :-
        "SmartModem V.32 M7F"
        A Series 4 will have this :-
        "SmartModem V.32bis M7F"

   3:   The third method is to look at the model number on the decal
        underneath.
        A Series 3 M7F has the model number SM7700
        A Series 4 M7F has the model number SM7710

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Q: I used the #J command to connect to a LAPM modem and it didn't
   disable LAPM.

A: The #J Command doesn't really disable LAPM itself, it only disables
   the LAPM detection routines and switches to LAPM regardless of
   whether it was detected or not. This command is necessary when
   connecting to some modems that do not support proper LAPM detection
   ie/ TR250s (Trailblazers).

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Q: I have an Amiga computer and every time I turn on Hardware flow control
   I suddenly can't talk to the modem anymore?

A: Some Amiga terminal programs require the DSR (Data Set Ready) pin to be
   high before it will transmit any data. You can do one of two things
   either switch the DSR inhibitor switch on the back of the modem down.
   Or set 'AT&S0'.

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Q: I can't connect to some modems in LAPM/MNP Auto-Reliable (\N3) mode
   even though these modems have MNP?

A: Some older MNP only modems do not handle the LAPM detect phase correctly
   and thus get confused. All you have to do is set (\N2) MNP Reliable or
   (\N7) MNP Auto-Reliable mode and you should be able to connect to these
   modems perfectly.

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Q: What is flow control?

A: Flow Control is a means of controlling the data movement between a PC
   and a serial peripheral (i.e. modem or Printer) so as to allow the data
   to be handled and processed at the speed that the device is capable of.

   i.e. using a Series 4 SmartModem at 14400 bps line speed but an interface
   speed (between modem & computer) of 38400. The data will be sent to the
   modem too fast for it to process, so flow control is used to prevent the
   data in its buffer being lost.

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Q: What is the S register 33 all about?

A: The Mysteries of S33:

   The value of S33 is used to determine two things, when to retrain, and
   when to disconnect. The modem needs to issue a retrain in order to detect
   loss of carrier (The other end hanging up).

   Setting S33 smaller ( ie 1 or 2) will cause the modem to retrain on
   smaller line disturbances but will decrease the possibility of missing
   a disconnect event.

   Setting S33 larger will make the modem less sensitive to line disturbances
   (and thus reduce the number of unnecessary retrains) but increase the
   possibility of missing a disconnect event.

   Setting S33 to 0 will disable retrains completely and will prevent the
   modem from disconnecting if the remote modem departs.

   Unfortunately not all telephone lines have the same charactistics and so
   the value of S33 may need to be altered to suit a particular line.

   It is not recommended that you change the default value of S33 unless
   you have a large problem with disconnects or a large numbers of unnessary
   retrains.

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Q: What are the Error Correction connect/fallback timings in the Series 4
   SmartModem?

A: In LAPM/MNP Auto-Reliable Mode (\N3)
   1.5 seconds of LAPM detect               : 1.5 Seconds
   2 MNP Detection Packets 2 seconds apart  : 4 seconds
   If a 'SYN' is detected, extend to 10 MNP Detection packets 2 seconds apart
   Fallback to Constant Speed mode

   In MNP Auto-Reliable mode (\N7)
   2 MNP Detection Packets 2 seconds apart : 4 seconds
   Fallback to Constant Speed mode

   In MNP Reliable Mode (\N2)
   15 MNP Detection Packets 2 seconds apart : 30 seconds
   Disconnect

   In LAPM Reliable Mode (\N4)
   10 seconds of LAPM detect                : 10 Seconds
   Disconnect

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Q: What is MNP10?

A: MNP10 is an integrated set of enhancements to achieve throughput on
   impaired lines.
   MNP10 Determines the optimal link speed for the line conditions.
   MNP10 Determines the optimal packet size for the line conditions.
   MNP10 over cellular links determine the optimal transmit level.
   MNP10 is continually updating the above during a connection.

   MNP10 provides, for the first time, an integrated suite of techniques
   to provide maximum throughput on impaired lines. It provides a means
   of ensuring that an error correcting link will be achieved and maintained
   over the most severely impaired lines where previous error correcting
   protocols would have failed. It will negotiate capabilities with the
   remote modem and then monitor the performance of the line, dynamically
   adjusting to the optimal link rate and packet size.

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Q: I sometimes connect with MNP4/v.42bis on to some non v.42bis modems?
   All I get is garbage on the screen.

A: Some brands of cheap Australian modems have a problem in the capabilities
   phase of the MNP handshake, and falsely return that they support v.42bis
   when in fact they don't. The only thing you can do when you encounter this
   kind of problem is turn compression off (AT%C0).

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Q: What do I do if I think my modem is faulty?

A: First. Go to the section in your manual titled "Technical Help".
   Follow the simple fault finding Flow Charts and tables.
   If you find that the fault still cannot be resolved then call
   your local NetComm Support (The numbers are at the top of this FAQ),
   and a Technician will organise for the modem to be returned and repaired.
   NOTE: If you do not get a return Authorisation number before
   returning the modem, you could be subject to the no fault charge
   if the modem was tested and found to be working correctly.

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RCS Information (Revision Control System) only useful for version tracking

$Id: netcomm.faq 1.1 1993/08/11 18:43:11 Anthony Exp $

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