Reverse polarity protection 2 (CB22140E)

This circuit has an improvement over the previous one as it also has an LED indicator for correct polarity.

Zener regulated power supply (CB24061E)
This circuit was obtained from the July 1970 issue of Radio Electronics magazine. Zeners are power...
Telephone Line Simulator (CB16790E)
This circuit allows you to simulate an analog telephone line for the repair and testing of...
Small Transistor Amplifier (CB1370E)
This small power amplifier makes use of an output transformer given its design time. In fact, the...