This alarm with automatic shutoff was found in the April 1975 Radio Electronics magazine. The activation time is given by C1 and R3. The alarm uses series and parallel sensors.
This circuit was obtained from a Popular Electronics of 1994. The magazine no longer exists in its...
This circuit is from Motorola documentation on 1976 power devices. SCRs are powered according to...
This latching alarm using SCR was found in a Popular Electronics from 1992. The circuit triggers a...