We found this circuit in a 1956 Sylvania publication. It serves to monitor telegraph transmissions being placed next to the transmitter. The circuit is indicated for the range of 80 and 160 meters.
This circuit with low impedance output and 900k input impedance was found in the October 1993...
This oscillator for Morse code training was found in a Popular Electronics from the 90s. The...
This is another one of the many debouncer circuits that the reader can find on this site, and it...