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.

LM3914 Moving Point Voltmeter (CB25450S)
We found this circuit in the March 1992 issue of Radio Electronics magazine. The circuit has a...
Adjustable Field Strength| Meter (CB5188E)
The circuit presented may use any general purpose transistor. The indicator is an LED and...
5 W Class Amplifier (CB13674E)
This unusual audio amplifier configuration was obtained in a 1974 documentation. The PNP...