We found this code key or coded keyboard in a publication from the 90s. The circuit uses components that are still common today and is powered by a 12 V voltage according to the relay used.
This flip-flop was found in an old documentation, being able to use transistors of general use...
The frequency of this circuit, that makes use of a tunnel diode as an active element, depends on...
This circuit is from Signetics' 80s documentation. The circuit generates 100 kHz signals according...