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 1987 signal injector included the power supply from the power grid. The transformer is 6 + 6...
This amplifier was found in a 70s documentation. The product gain x bandwidth is 350 MHz. The...
This simple receiver with junction FET uses a high impedance magnetic earphone (over 2 k). Power...