This two-tube circuit, one being a double, was found in Radio Electronics magazine from July 1958. The distance to the microphone depends on noise and losses. The cable must be shielded.
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...