This circuit was obtained from an American technical manual from the 80's. The integrated circuit is an operational of the time that can be replaced by a modern equivalent.
This different alarm system, found in an old publication, uses the starter chain to protect the...
We can implement this circuit from a 1994 publication using BC548 and BC558 transistors. The...
Found in an English documentation, this circuit provides a 50 Hz signal according to the local...