We found this circuit in an American documentation from the 90's. The circuit makes use of general purpose NPN transistors. The 0.005 uF (5nF) capacitors determine the frequency.
This circuit was found in old American documentation. Transistor is general purpose and relay is...
This simple alarm with latching uses a relay as the main element. The circuit is from a Radio...
This circuit is from an Italian publication called Fare Elettronica from 1987. What we have is an...