In this circuit of an American documentation of the 90s, when the light is cut, we have the production of a pulsating tone. R3 determines the trigger sensitivity.
This 1-transistor Hartley oscillator generates an audio signal that is dependent on capacitor C1....
This modulator circuit can be used in AM transmitters up to about 10 W of power. The TDA2002 must...
This 1969 Electronics World power supply has 5 V to power digital circuits and a 170 V output for...