This two-tone alarm siren was found in the January 1975 issue of Radio Electronics magazine. The power transistor can be changed and with it, Rx has values from 10 to 47-ohm.
This basic circuit was found in the March 1998 issue of Electronics Now magazine. The circuit is...
This buzzer trigger can be used for small alarms. We find it in an 80’s American documentation. The...
This simple circuit was obtained from Popular Electronics in December 1990. The magazine no longer...