Remote control tester (CB7823E)

This circuit from a 90s Electronics Now, uses a 4010 gate as a signal amplifier. The circuit triggers an indicator LED.

DC Motor Digital Inverter (CB18010E)
This circuit, which can also be adapted to function as a microcontroller shield, is from 2003...
Humidity Relay (CB18619E)
This moisture-activated relay was obtained from an American documentation from the 1980s,...
High Overvoltage Band Pass Filter (CB19685E)
This circuit was found in a documentation of the 80's having characteristics of high overvoltage given by...