This circuit has the intensity of the signals controlled by the light that falls on the sensor. Note that it is not a frequency-controlled oscillator. Equivalent transistors can be used.
This circuit was found in Radio Electronics magazine from October 1966. It consists of a rhythmic...
This circuit is from a Popular Electronics from the 90's. The circuit provides an output for a...
The transformer of this unit found in an old Japanese documentation can have 22 to 25 V of...