Motorcycle headlight monitor (CB9117E)

This simple circuit was found in Popular Electronics from the 1980s. The circuit uses an LED as an indicator.

Flip Flop with the Operational LM3900 (CB4510E)
Other series amplifiers such as the MC3301, MC3401 and LM2900 can be used on this circuit. We...
Bistable 555 and 4013 (CB17031E)
This configuration, widely used in our articles and on this website, uses a 555 to control a relay...
Simple Biofeedback 4046 (CB18467E)
This circuit was found in an English documentation from the 90s. It uses a PLL CMOS 4046 and is...