This circuit triggers an LED when the input signal exceeds the peak, or the value set in RV1. The transistors can be the modern equivalents BC549.
This circuit was suggested by Sprague Electric in an 80's documentation. The circuit uses a...
This circuit was found in a Radio Electronics from June 1967. The regulator is suitable for power...
This circuit is designed to be used with the infrared transmitter two circuits before this one....