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.
Using one unijunction transistor and two bipolar transistors, this circuit generates a signal from...
This circuit is from a 1995 documentation. Several CMOS integrated circuits are used to produce...
This sequential circuit with an optical coupler was found in a Popular Electronics from the 90s to...