This circuit is for a siren that can be used with any of the above alarms and also other types. The circuit is from a Radio Electronics magazine from May 1975.
We found this interesting timer circuit or CMOS timer in a 1988 publication. The circuit is still...
This circuit can be powered by 2 or 3 small batteries. The resistor can have values between 220...
Found in a magazine 73 for radio amateurs, this circuit operates in the 144 MHz band, at a...