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 shows how a monostable can be obtained from an RS flip-flop using a unijunction...
This circuit was found in an application note of the LTC1164 from Linear Technology of the 1990s....
Using a general-purpose transistor this AC amplifier was found in the November 1993 issue of...