A MODulator/DEModulator translates digital information from your computer intoacoustic tones that can be sent and received, from modem to modem, viastandard telephone lines.Atari produced several modems for use with the 8-bit Atari computers:Atari 830 Acoustic Modem:    ( = Novation 'CAT' )- a stand-alone, acoustically coupled, frequency shift keying (FSK) modem- up to 300 bits per second- Bell 103/113 modem compatible- requires Atari 850 Interface Module or equivalentAtari 835 Direct Connect Modem:   (by Racal-Vadic?)- 300 bps- Bell 103/113 modem compatible- pulse dialing- 2 SIO ports- packaged with the TeleLink II cartridgeAtari 1030 Modem with ModemLink Telecommunications Program:  (by Penril)- 300 bps- Bell 103/113 modem compatible- built-in ModemLink software.- 2 SIO portsAtari XM301 Modem:- 300 bps- Bell 103/113 modem compatible- with XE Term disk software (developed by Russ Wetmore for Atari)- permanent SIO cable, must be at end of SIO chain- draws its power from the computer via SIOAtari SX212 Modem:- SIO & DB25 RS-232 serial ports, must be at end of SIO chain- 1200 baud- Bell 103/113/212A modem compatible- SX Express! disk software (developed by Keith Ledbetter for Atari) to be  sold separately, packaged with an SIO cable.- Key engineer/designer: Jose Valdes at Atari