This alarm is either activated or triggered after a certain amount of time, giving the owner time to exit or enter and disarm it. The circuit is from a Radio Electronics from April 1975.
This half-wave control was published in the September 1987 issue of Radio Electronics magazine. The...
This circuit can be enabled and disabled by a TTL signal. The relay is a low current reed type and...
This circuit is from the time when the 741 was first introduced. It was published in the February 1971...