This circuit is from a 1972 Motorola publication. The used transistor can still be found, but it can be used equivalent. The circuit is powered by the amplifier with which it must operate.
This circuit is from a 1976 documentation. It provides a pulsating DC voltage that can be varied...
The presented circuit triggers the relay when S is pressed for an instant, keeping it in these...
This circuit is from a Radio Electronics from October 1963. The LDR and transistors are from the...