Maybe take some kind of modem chip, which will output, typically a 3+KHz bandwidth, then frequency shift the resulting signal up to 22-25KHz or so. Bob Ammerman RAm Systems (contract development of high performance, high function, low-level software) ----- Original Message ----- From: Richard Sloan To: Sent: Tuesday, February 06, 2001 10:29 AM Subject: [EE]: best method to add data stream to audio channel I would like to inject data into a line level audio signal and recover it at the other end, of course you do not want to hear it and I am also limited by bandwidth of 20-20k, as this audio channel does get wirelessly transmitted. I may have some headroom and be able to put it at say 30K, what would be the best encoder/decoder pair? Datarate required 19200bps Richard. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads