The CMX624 Bell 202 and V.23 modem provides full duplex 1200bps data signaling suitable for telephone based information and telemetry systems where low power operation is desired. Bell 202 and V.23 signaling delivers fast call set up times and robust, error resistant, transmission in 2 or 4 wire line circuits. A rich set of important additional functions enhances end product value while reducing size. These include: integrated DTMF encoder for dial out functions, single tone encoder for `melody' generation, answer tone generator/detector, line reversal and ring detector for `waking' up a sleeping C, adjustable Tx and Rx gain, and a low impedance pull down output for hook relay control. The addition of the answer tone generator/detector and call progress tone detector makes the set-up of a telephone call much easier for the host C to accomplish.