We found this circuit in the November 1974 Radio Electronics magazine. The capacitors determine the output time, and it is normal to obtain 1 second for each uF used.
This circuit, found in a 1986 documentation, uses an optical sensor to count pulses and, in its...
This circuit, found in a 1997 publication, activates a lamp or a monitoring camera when the bell...
We found this circuit in an English publication in 1981. It can be improved by exchanging T1 for a...