This conventional relay light detector circuit uses a 741 as a voltage comparator. The sensitivity adjustment is made in R1. The supply voltage depends on the relay used.
This frequency band below 15 kHz converter was found in a Popular Electronics from the 90's. The...
The circuit presented is a 10 MHz oscillator with crystal, which already has several splitters for...
We found this circuit in the November 1992 issue of Radio Electronics magazine. The circuit has...