MM74HC942

MM74HC942 300 Baud Modem January 1988 MM74HC942 300 Baud Modem General Description The MM74HC942 is a full duplex low speed modem It provides a 300 baud bidirectional serial interface for data communication over telephone lines and other narrow bandwidth channels It is Bell 103 compatible The MM74HC942 utilizes advanced silicon-gate CMOS technology Switched capacitor techniques are used to perform analog signal processing MODULATOR SECTION The modulator contains a frequency synthesizer and a sine wave synthesizer It produces a phase coherent frequency shift keyed (FSK) output LINE DRIVER AND HYBRID SECTION The line driver and hybrid are designed to facilitate connection to a 600X phone line They can perform two-to-fourwire conversion and drive the line at a maximum of 0 dBm DEMODULATOR SECTION The demodulator incorporates anti-aliasing filters a receive filter limiter discriminator and carrier detect circuit The nine pole receive filter provides 60 dB of transmitted tone rejection The discriminator is fully balanced for stable operation Features Y Y Y Y Y Y Y Y Y Y Drives 600X at 0 dBm All filters on chip Transmit level adjustment compatible with universal service order code TTL and CMOS compatible logic All inputs protected against static damage g 5V supplies Low power consumption Full duplex answer or originate operation Analog loopback for self test Power down mode Applications Y Y Y Y Y Y Y Y Built-in low speed modems Remote data collection Radio telemetry Credit v...