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.
This amplifier for small cassette tape players was found in an English documentation from 1969. The...
This circuit is intended to trigger a TTL door or flip-flip from a signal coming from an SCR....
We find this circuit in a 1980s documentation. The circuit can be applied to modern operators with...