The modem includes a programmable single/dual tone transmitter, a programmable DTMF receiver, three programmable tone detectors (which operate concurrently with the V.21 Channel 2 receiver), and a ring detector. The transmit output level is also programmable. Voice and Audio Codecs (-V Option) The voice coder/decoder (codec) compresses voice at an average rate of 2.9 kbps or at a fixed rate of 4.7 kbps with near toll quality playback at various pitch synchronized playback speeds. An average rate of 2.9 kbps provides 24 minutes of stored voice messages in 4 Mbits of memory. This voice codec allows the host controller to efficiently store and playback digital incoming messages (ICMs) and outgoing messages (OGMs). The ADPCM audio codec compresses audio signals (music/voice) at 32 kbps or 24 kbps for highest fidelity coding and reproduction. The PCM audio codec allows the host controller to transmit and receive uncompressed audio signals.