Mini Megaphone (CB8952E)

Found in Popular Electronics' 90s, this small megaphone is based on LM386. The circuit uses a high impedance microphone.

2 transistor radio (CB22272E)
We found this circuit in an American documentation from the 60's. The transistors are made of...
Digital Capacimeter (CB4312E)
The accuracy of this circuit depends on adjustments made with capacitors of small tolerances of known...
OR function with Relay (CB19773E)
The figure shows how to implement an OR function with two inputs, using a relay. The relay...