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Recordings of modem conversations

eeguru

Veteran Member
Joined
Mar 14, 2011
Messages
1,618
Location
Atlanta, GA, USA
A rather odd request indeed. But I was wondering if anyone knew of a data repository of recordings of telephone conversations from modems? I really don't care about modulation scheme as long as it's not a simple FSK; basically any ITU-T V.spec standard (V.22 and up). I need both the startup negotiation tones with as much of the following data exchange as possible. And preferably both transmit sides isolated but I can probably tell which side is talking as I get into it.

I know I can setup two modems and just record the conversation with a microphone. But a raw capture of the 64KBit u-law or a-law PCM would be swell. Especially if I could 'see' the echo and AGC measurements taking place in the negotiation.
 

kyodai

Experienced Member
Joined
Jan 26, 2011
Messages
467
Location
Kerpen, Germany
Why use a microphone? With a soldering iron you could directly connect the modem cable to a microphone line socket and record yourself at a lossless quality. =)

I have spent some time with the exact opposite, so instead of recording a modem conversation i actually emulated one from a sound card. I still have some win32 binaries i wrote to emulate american and German line tones (emulating a "line free").

If a simple handshake is enough for you (Most modem software shut off the speaker after that) then youtube is your friend...

https://www.youtube.com/watch?v=p8XKhCfsTts


With some graphics explaining a dial-up handshake:

https://www.youtube.com/watch?v=abapFJN6glo
 

vwestlife

Veteran Member
Joined
May 2, 2008
Messages
5,178
Location
central NJ
Some "voice"-equipped internal modems have an audio output using the same kind of connector as a CD-ROM drive's analog audio output, which you can connect your sound card's voice input, if it has one -- or to its CD audio input, if it doesn't. (Now you know what that seemingly useless "voice" slider in your Windows mixer is for! Likewise, if you see a "video" slider in the mixer, that was intended for use with a hardware MPEG decoder board, to enable DVDs to be played before CPUs were powerful enough to do the MPEG decoding in software.)
 
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