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 operational amplifier configuration has gain controlled by an external voltage applied to a...
This circuit was found in an American 1980s documentation. Dual FETs can be replaced by single...
This circuit with an integrated circuit of the time was found in the magazine Radio Electronics of April...