The CMX867 is a multi-standard modem for use in telephone based information and telemetry systems. Control of the device is via a simple high speed serial bus, compatible with most types of C serial interface. The data transmitted and received by the modem is also transferred over the same serial bus. On-chip programmable Tx and Rx USARTs meeting the requirements of V.14 are provided for use with asynchronous data and allow unformatted synchronous data to be received or transmitted as 8-bit words. It can transmit and detect standard DTMF and modem calling and answer signals or user-specific programmed single or dual tone signals. A general purpose Call Progress signal detector is also included. Flexible line driver and receive hybrid circuits are integrated on chip, requiring only passive external components to build a 2 or 4-wire line interface. The device also features a Hook Switch Relay Drive output and a Ring Detector circuit which continues to function when the device is in the Powersave mode, providing an interrupt which can be used to wake up the host Controller when line voltage reversal or ringing is detected. The CMX867 operates from a single 2.7 to 5.5V supply over a temperature range of -40C to +85C and is available in 24-pin TSSOP, SOIC and DIP packages.