In order to answer these questions a bit more and start learning programming, [Nakazoto] built a 10-bit binary adder with relays ... a carry register board and a 1-bit ALU board.

Full adders can add three binary digits or bits. The binary addition of two bits produces two numbers: the sum of the added bits and a carryover bit that is then added to ... 3.3 V, -3 V, 1.2 V, 1.5 V ...