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 is the traditional voltage follower configuration with the 741 operational amplifier. The...
S The purpose of this circuit, found in a 1975 publication, is to suppress the noise that occurs when...
In the figure we have the way to trigger a 7555 CMOS monostable with a positive pulse. The time...