Circuits similar to this can be found in this section. This is from 1967 General Electric documentation. The main SCR must be fitted with a heat sink.
This circuit has a start and reset switches and can generate signals at long intervals determined by the...
Found in a Popular Electronics from the 90s, this circuit uses a double 555 to emit beeps when the...
The components used in this 80's circuit are not common today. The circuit is very sensitive and must...