Light test (CB8789E)

This light-sensing probe was found in a 90s Popular Electronics. The circuit detects light sources by triggering a buzzer.

Zener Tester (CB24999E)
The purpose of this circuit, which we found in the November 1986 Radio Electronics issue, is to...
Low Noise Crystal Oscillator (CB6151E)
This circuit was found in an 80's Electronic Design. The frequency depends on the crystal and the...
Switching Regulator (CB5450E)
This switching regulator circuit with less than 100 mV ripple was found in a 1980s documentation. The...