Dial Up Modem Sounds: x2
Here's the US Robotics standard for 56K, before V.90 was adopted by the industry: x2
Upcoming modulations: K56Flex, and Telebit Trailerblazer PEP
If there's something else you'd like to hear, leave me a comment and I'll see what I can do.
Originating modem: US Robotics Courier V.Everything
Answering modem: US Robotics Netserver/8 I-Modem
Call path is as follows:
Courier V.Everything -- FXS port on Cisco IAD2431-16FXS -- PRI port on VConsole 8BRI-U-MOD-2PRI -- Dialogic Diva 4BRI-8 in an Asterisk server -- VConsole 8BRI-U-MOD-2PRI -- US Robotics Netserver/8 I-Modem
The Asterisk server records the call, putting the caller in the left channel, and the answerer in the right.