This interesting circuit uses a sodion valve that we have already described in an article on the website. The circuit uses several batteries for power. The phone is of high impedance.
In this circuit, the current capacity doubles, but is still of the order of microamps. The...
We found this oscillator in an integrated circuit manual from the 90's. The circuit shows how to...
This regulator can be controlled by a logic signal. The circuit is from an Electronics Now from...