More inputs can be added to this adder that we found in the January 1995 Electronics Now magazine. Other operational ones can be used.
This circuit is based entirely on SCRs. The circuit is from an American 80's documentation; and the PUTs...
This circuit is used in transceivers, enabling input selection by diode switching through polarity...
This 80's circuit uses a small light bulb as an indicator, but an LED with the appropriate resistor...