Found in American documentation from the 1980s, this circuit has a diode feedback. At the exit we have an indicator LED. The LM3900 is a transconductance operational amplifier.
This audio-driven relay was published in the July 1977 issue of Radio Electronics magazine. The...
This circuit can be used for signaling a panel with a common incandescent lamp. The lamp will...
This crystal oscillator is indicated for the calibration of IF steps of common radio receivers. The...