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.
We found this circuit in a 1967 Electronic Design. The circuit used a MOSFET of the time, which is...
This circuit uses an audio output transformer found in old transistor radios. Power output is...
This sensor circuit for a small robot was found in a Popular Electronics from the 90s. The circuit...