We found this circuit in the July 1969 Radio Electronics magazine. The circuit uses a coupler made with a lamp and an LDR. The power of the lamp determines the types of diodes.
This 4-digit counter, using CMOS technology, was found in a 1997 documentation. The circuit is...
This circuit activates a relay that has a lamp as a load. The circuit is from a Radio Electronics from...
This circuit can measure frequencies up to just over 1 MHz and uses CMOS technology. The circuit is...