Ultrasonic Proximity Sensor (CB21312E)

This circuit was found in a Popular Electronics from the 90s. The circuit uses a ceramic capsule as an emitter and detector.

Telephone Line Test (CB24950E)
This circuit for testing old analog lines was published in April 1986 Radio Electronics magazine. The...
Soft Start 15 V regulator (CB20800E)
Found in documentation from the 1980s, this circuit applies to other 3-terminal voltage...
Electronic Foosball Scoreboard (CB16393E)
This circuit was found in a 1981 documentation. As you can see, this is a well-designed automatic...