This circuit is from Radio Electronics from March 1977. The integrated circuit is from that time and the circuit is intended for an infrared audio link. The modulation is in pulse frequency.
For those who like experimental circuits, here is a sequential flasher system with LEDs, which can be...
This circuit can be used in broilers, greenhouses, drying chambers to regulate the temperature in a simple...
This circuit consists of an electrostatic sensor that can check if a cable is energized by simply...