This circuit converts a high voltage into a frequency using an optical coupler. The transistor can be 2N2646 and the coupler admits equivalent. The circuit is from a 1974 publication.
We found this circuit in the May 1990 issue of Radio Electronics magazine. The circuit is powered by...
Found in Radio Electronics from the 90s, this circuit is based on the 555 directly feeding a small...
This circuit converts sinusoidal signals into squares and can be powered by voltages from 1.5 to 5...