This ingenious circuit was found in a 1990s Popular Electronics. The oscillator is a 555 and the keyer uses an optocoupler in the configuration shown.
We found this simple warning circuit for car blinkers (arrow) in a 1987 publication. The relay must...
Based on common operational amplifiers, this circuit was found in Texas Instruments documentation. The power...
This circuit, found in US documentation, can measure the power of transmitters up to 10 W, given...