MM74HC942 300 Baud ModemGeneral Des criptionThe MM74HC942 is a full duplex low speed modem. It providesa 300 baud bidirectional serial interface for data communicationover telephone lines and other narrow bandwidthchannels. It is Bell 103 compatible.The MM74HC942 utilizes advanced silicon-gate CMOStechnology. Switched capacitor techniques are used to performanalog signal processing.MODULATOR SECTIONThe modulator contains a frequency synthesizer and a sinewave synthesizer. It produces a phase coherent frequencyshift keyed (FSK) output.LINE DRIVER AND HYBRID SECTIONThe line driver and hybrid are designed to facilitate connectionto a 600X phone line. They can perform two-to-fourwireconversion and drive the line at a maximum of 0 dBm.DEMODULATOR SECTIONThe demodulator incorporates anti-aliasing filters, a receivefilter, limiter, discriminator, and carrier detect circuit. Thenine pole receive filter provides 60 dB of transmitted tonerejection. The discriminator is fully balanced for stableoperation.FeaturesY Drives 600X at 0 dBmY All filters on chipY Transmit level adjustment compatible with universalservice order codeY TTL and CMOS compatible logicY All inputs protected against static damageY g5V suppliesY Low power consumptionY Full duplex answer or originate operationY Analog loopback for self testY Power down mode