Light beam switch (CB21413E)

This circuit was obtained from a 1965 General Electric SCR manual. The components are from the period.

Simple Multimeter (CB16271E)
The assembly of a good multimeter meets only one obstacle: the precision that is obtained depends on...
Broadband amplifier (CB8402E)
This circuit that can amplify signals from 0 to 30 MHz was found in a 90s Popular Electronics....
Simple Sound Shield (CB19764E)
PWM signals can be used to produce sounds in a microcontroller. This circuit allows sounds to be...