This circuit is from an American manual from 1975. The transistors are types of the time, but equivalents can be used, as well as the relay that can be according to the supply voltage.
This configuration is from the 70s, having been found in an American documentation. The...
This circuit was found in the August 1992 issue of Radio Electronics magazine. The circuit can be...
This simple test tells you whether a PNP or NPN transistor is OK. The signal is given by turning on...