Found in a 1969 British publication, this circuit uses a regenerative switch with two transistors to produce pulses that depend on C1. The relay must be in accordance with the supply voltage.
This circuit was found in a National Semiconductor manual from the 1970s, appearing in articles and on...
This circuit was obtained in an American documentation from the 80's. The transistors can be...
In this version from the 60s, the indicator is a light bulb, but the circuit can be modernized with the...