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 can be used with the CIR12053 receiver or with others shown in this section of the...
When the input of this circuit goes to high level, the LEDs start to flash alternately. The...
This circuit is from a 1965 Radio Electronics. The triggering transformer generates high voltage...