Path: utzoo!attcan!uunet!hayes!tnixon
From: tnixon@hayes.uucp (Toby Nixon)
Newsgroups: comp.dcom.modems
Subject: Re: Recording of Modem output
Message-ID: <1856@hayes.uucp>
Date: 8 Oct 90 10:47:33 GMT
References: <1990Oct6.114313.9227@wubios.wustl.edu>
Organization: Hayes Microcomputer Products, Norcross, GA
Lines: 34

In article <1990Oct6.114313.9227@wubios.wustl.edu>,
phil@wubios.wustl.edu (J. Philip Miller) writes: 

> I would like to know if it is possible to record the output of a modem and
> later play it back into the modem and recover the original digital signal?
> ...
> My recollection of the technology would suggest that it would be easiest to do
> with the FSK of 300 baud modems (which would be plenty fast enough for my
> application) technology.

You're on the right track.  You should be able to record and play 
back an FSK signal.  PSK, QPSK, or QAM (the modulation schemes used 
in higher-speed modems) probably couldn't be done that way, 
primarily due to the more complex initial training that must take 
place between the modems (the timing of which would be virtually 
impossible to get right on a recording).

> Has anyone done this?  If so what did you have to do to connect the modem to a
> recorder?  Since a phone line normally has a voltage, does one have to be
> supplied?

I believe Radio Shack sells devices that allow you to connect a 
recorder to a phone line.  You don't have to worry about the line 
voltage; a modem supplies it's own (unless you use one of the new 
line-powered modems, but you don't want to do that for this 
application).

	-- Toby

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