This Public Address amplifier was found in an American publication from 1947. The circuit uses 5 tubes and a transformer source.
Vz determines the trigger point for this protection circuit. The SCR doesn’t need to be mounted on a...
Varicap or varactor is the basic component used in this circuit of an American 80's documentation. The...
In this alarm R1 and R2 can be 10k. The SCR is any 106 Series SCR and V1 is an oscillator buzzer....