This 1977 circuit only allows the solenoid to energize if the right combination of switch positions is selected. The relay is 6 or 12 V depending on the low voltage supply used.
This circuit was found in Radio Electronics from the 90s. The components used are common, and the...
This circuit was found in an American publication called Ham Radio. The circuit uses still current...
This circuit was obtained from a 1997 publication. It is an alarm that has a lock and a bistable...