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.

CMOS Touch Switch (CB12091E)
This circuit, obtained in a 1983 magazine, can drive loads up to 100 mA if the transistors are...
Monostable LM139 (CB15529E)
It is possible to design a monostable multivibrator around a voltage comparator of the four...
Voltage inverter (CB23691E)
This voltage inverter circuit is from a Radio Eklectronics from October 1965. It was used in...