This is the receiver from the previous alarm system. The circuit is from Radio Electronics, April 1989, and has an LDR as the sensor. Optical devices should be used to improve performance.
This circuit was obtained in a 1989 English magazine. Despite using a fixed 5 V regulator, it can...
With the feedback of the output circuit, the monostable acts as a frequency divider, that is, it...
In this circuit of an old American documentation, the input impedance is the same as the output...