This circuit is from an old American documentation using as indicators for the flip-flops neon lamps. This way, the circuit has two supply voltages.
This circuit was found in a Mullard transistor manual from 1960. Note the symmetrical power...
With the shadow over the sensor, it is possible to interrupt the sound of your amplifier using this...
This circuit puts the battery in the circuit when the voltage of a source is cut, preventing it...