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 an old American documentation. Its purpose is a proportional scanning signal...
This circuit emits a loud sound in a headset when the driver who wears it nods while being in a...
This amplifier stage was found in a 1956 Sylvania manual and has an unusual configuration with a...