This circuit was found in a documentation for radio amateurs from the year 70. Its purpose is to produce a tone on a transducer when transmitting messages in SSB telegraphy.
This old receiver (1967) uses germanium transistors from the time and coupling transformers,...
This circuit can act as a shield being controlled by a microcontroller by pin 1 or 2. The...
A negative pulse applied to the input of the circuit shown in figure bellow turns on the relay....