This circuit was found in the September 1971 Radio Electronics magazine. The buzzer can be replaced by a relay according to the supply voltage. R1 adjusts the sensitivity.
This latching alarm circuit using relays was found in American documentation. Sensors are...
Pressing and releasing S1 remains one of the neon lamps. Which one will be, it is not possible to...
Found in an Electronic Design, this small power source uses a battery as a voltage reference,...