Richard, the first half of your requirement, to inject a 19200 datastream onto a bandlimited 20khz channel and also "not" hear it does not sound very straightforward. As Bob indicated, you may be able to get by by extending the channel BW, and shifting the datastream up above the human hearing range. Also, you might do a search on modems and other devices that combine voice and data onto one channel. I am not sure, but believe some of these devices use a form of time-multiplexing where data and voice are alternated in time over the same bandwidth channel. However, to do this for your particular requirements, you may have to employ data compresison techniques with either/both the voice/data. - danM ===================== At 11:20 AM 2/6/01 -0500, you wrote: >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