A while back there was some interest in DTMF decoding I found the following URL www.interstice.com/~sdattalo/technical/theory/dtmf.html This may be of interest. Norman PCS Engineering Norman Gillaspie 325M Sharon Park Dr. #210 Menlo park, Ca. 94025 Tel 650-854-5263 Fax 650-854-5445 Email norman@pcseng.com