In the figure we have a basic shield circuit with TTL to TTL optical isolator. For the emitting LED the voltage can be different from 5 V.
Originally, this circuit was created to monitor the liquid level in the reservoir of a car's...
This circuit for the two-meter band of radio amateurs was found in 1980s documentation....
This circuit is from a Motorola documentation from 1968. The integrated one is an operational of...