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 two transistor preamplifier is intended for the use with three terminals electret...
This circuit was obtained from an American publication of the 80's. The integrated circuit is of the...
This circuit can operate with signals from 1.5 to 150 MHz. C1 is 36 pF and C2 is 4n7. The diode...