We found this circuit in a Radio Electronics from the 90s. Transistors admit current equivalents, especially the power one that is not a common type today.
This 1995 circuit uses interruption sensors or NC connected in series in any quantity. With the...
This circuit transmits the audio signals from a telephone line to an FM receiver placed nearby. The...
This circuit is from an old manual of operational amplifiers. The setting can be adapted to work...