Found in 90s Popular Electronics, this circuit produces a modulated infrared beam for a remote phone whose circuit is shown right after it. Infrared LEDs are common.
This circuit, suggested by an Electronics World of 1969, keeps a blinking LED for a while when a...
This is a Philips commercial circuit from the 90s. The integrated circuit must have a good heat...
This circuit converts a signal from any waveform into a rectangular or square signal of the same...