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.
Although it is a common configuration today, these circuits were taken from an old publication. The...
This circuit can be used with any auio amplifier, converting it into a AM receiver. Antenna is a...
This non-inverter circuit was found in a Radio Electronics. It shows the basic configuration of a...