We found this circuit in a Radio Electronics magazine from November 1976. The clock frequency is divided by 10 and the maximum value depends on the integrated circuits used.
With this circuit, from an old operational datasheet, it is possible to measure the CMRR,...
Found in a Popular Electronics from the 90s, this circuit can be adapted to use LEDs. The power...
The circuits shown in the figure, that of an infrared video signal transmitter and receiver, were...