We found this circuit in the October 1996 Electronics Now magazine. The circuit uses LDRs as sensors and drives relays. The relays must have voltages according to the power supply.
This detector or window discriminator was found in an old American manual. Comparators or...
The output voltage depends on the zener diode. Zener in the range between 1.2 to 12 V rated to 1 W...
This circuit uses a 100 kHz crystal, but nearby frequencies can be obtained with appropriate...