This circuit is based on the light comparison of two LDR sensors. We found it in a 90s Popular Electronics. The transistor must be according to the indicator or load being driven.
Crystals from 100 kHz to 1 MHz can be used in this 1957 Raytheon circuit. 4 can have values...
Assembled with SMD components this circuit can be very small. The range is a few tens of meters. We...
This circuit can provide a voltage of up to 900 V depending on the input voltage. The diodes must...