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.
We found this circuit in an English documentation from 1979. It shows how you use a 100 uA...
This circuit was found in an EDN from the 90s. For the components indicated, the frequency is 10 kHz....
This is a very interesting automation that can be adapted for other types of applications. In...