The CMX644A Bell 212A / V.22 modem provides full duplex 1200bps data signaling suitable for telephonebased information and telemetry systems where low power operation is desired. Bell 212A / V.22 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.