Found in a 1980s documentation, this circuit uses transistors from that time. Modern equivalents can be used. The alarm is a piezoelectric buzzer with na included oscillator.
We found this simple operating tester 741 in a European publication in 1991. The circuit...
In this receiver the is formed by 80 turns of wire 28 or close in a ferrite rod. The handset is...
The use of a diac improves the performance of the two dimmers in the previous circuits. The...