DESIGN PRECAUTIONS

Power supplies to digital systems may contain high ampli-

tude spikes and other noise To optimize performance of the

MM74HC942 operating in close proximity to digital systems

supply and ground noise should be minimized This involves

attention to power supply design and circuit board layout

Power supply decoupling close to the device is recommend-

ed Ground loops should be avoided For further discussion

of these subjects see the AudioRadio Handbook published

by National Semiconductor Corporation

Interface Circuits for MM74HC942 300 Baud Modem

TLF5348 – 4

Complete Acoustically Coupled 300 Baud Modem

TLF5348 – 5

Note

The efficiency of the acoustic coupling will set the valves of R1 and R2

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