This circuit for very long-time intervals was found in the March 1993 Radio Electronics magazine. Times of several days or even weeks can be achieved depending on the value of C1.
In the figure we have the shot made by an interrupted light beam using a phototransistor or a...
Using a CA3130 operational amplifier, this circuit from a 1977 documentation can handle low...
This is the receiver for the CB1364E transmitter. Other receivers can be found in this section of...