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.
Analyzing the circuit shown in the figure we see that the difference in relation to the others is in...
With this circuit, we can have a remote frequency control of a tuned circuit. Lx is the coil of...
This mains-synchronized circuit produces a simple 1 pulse per second. The circuit is from a Radio...