Date: Mon, 10 Apr 1995 08:44:01 -0500 (CDT) From: Guy Helmer <ghelmer@alpha.dsu.edu> To: M C Wong <mcw@hpato.aus.hp.com> Cc: freebsd-questions@freefall.cdrom.com Subject: Re: more modem question Message-ID: <Pine.OSF.3.91.950410081542.23070A-100000@alpha.dsu.edu> In-Reply-To: <199504100629.AA207245387@hp.com>
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On Mon, 10 Apr 1995, M C Wong wrote: > Hello comm and modem gurus, > At various time I see lots of mentiond about setting the modem in > fixed speed mode. Can someone explain to me what exactly does it mean by > fixed speed more ? Also, does it refer to fix modem between modem and > modem, or modem and a DTE ? Also, does this 'fixed speed' mode only have > meaning with dial-in or applies to modem used for dial-out ? I think you are referring to a configuration which applies to the speed of the DTE-DCE interface between the computer and the modem when used for dialup purposes. In this config, the two modems communicate with each other at whatever speed they agree upon, but the dialin-modem to computer interface stays at a fixed speed. The benefit of this configuration for a dialin system is that the remote user sees a login: prompt immediately regardless of the speed used by the modems. In the (IMHO) more typical matching-speed configuration, getty on the dialin system tries giving a prompt, then watches for junk characters/BREAKs/NULLs; if it sees something like that, it goes to the next speed (configured via nx= entries in /etc/gettytab) and gives another login prompt. Because of this sequence, a remote user needs to know that if they see "garbage" on the screen, they should press <Enter> or send a BREAK until they see a good login: prompt. The dialing modem and computer may also communicate with each other at a fixed speed, but that would probably be to take advantage of compression (MNP or V.42bis) in the modem-to-modem protocols. > Finally, what is the AT commands to set up my modem for fixed speed > at 38400 or in general at speed X ? Does it require the DTE connected to > it be set to the speed X and issue &W0&W1 command ? I can't seem to > find any relevant command for setting this 'fixed speed' thingy. It seems to depend greatly on your modem. Perhaps look for something in the documentation refering to "locking-speed", "fixed serial port speed", or "serial port speed select". I would assume that it would require that your DTE be set at speed X and you would issue your modem's "commit to NVRAM" command(s). > Thanks in advance. Hope this helps, Guy Helmer Guy Helmer, Dakota State University Computing Services - ghelmer@alpha.dsu.edu
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