This circuit is from an American 80's documentation. The circuit indicates when the voltage of a 9 V battery drops below 7 V. The transistors can be BC548.
This two-transistor constant current source is from a 1968 documentation. Modern equivalent...
This circuit was obtained in a 1977 technical documentation. The PUT admits equivalent and the...
We found this circuit in a 1997 documentation. Its purpose is to turn a load on or off using...