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.
In the figure we have a piezoelectric transducer drive circuit that can be used in conjunction with the...
This circuit is from a Ferranti publication of 1968. The circuit generates a signal according to the...
This is one of the possible triac power control configurations using as a trigger element a...