Found in Motorola documentation from the 1970s, this circuit makes use of period components. The lamp is used as a stabilizing device. The signal is sinusoidal.
This simple voltage-controlled oscillator generates signals from 300 Hz to 1,500 Hz with voltages from...
When light fails to focus on the sensor, a common photo-transistor, the relay closes its contacts....
This variable oscillator with crystal was found in a Popular Electronics of the 90s. The circuit uses...