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.
This circuit uses two Raytheon RC4558 operational amplifiers that are similar to the 741. The...
This small stereo amplifier for headphones was found in a documentation on integrated circuits from...
This is a MOSFET version of a grid dip meter for frequencies between 1.8 MHz and 150 MHz,...