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.
This configuration from a 1976 technical documentation shows how to use a varicap in a direct...
This circuit for three-phase motors was found in a 1997 documentation. The circuit reverses the...
We found this circuit in a 1982 documentation, but the circuit can still be easily assembled, as the...