Thus relay O-2 is energized; it receives current because contact C5-2 is closed. And relay O-1 is not energized; it receives no current since contact C5-1 is open. So we have actually transferred information from the C5 register to the O register.
The same process in principle applies to all transfers:
The pattern of electrical impulses, formed by the positioning of one register, is produced in the positioning of another register.
SIMON’S COMPUTING AND REASONING
Now so far the computing registers in Simon are a mystery. We have said that C1, C2, and C3 take in numbers 00, 01, 10, 11, that C4 takes in an operation 00, 01, 10, 11, and that C5 holds the result. What process does Simon use so that he has the correct result in register C5?
Let us take the simplest computing operation first and see what sort of a circuit using relays will give us the result. The simplest computing operation is negation. In negation, a number 00, 01, 10, 11 goes into the C1 register, and the operation 01 meaning negation goes into the C4 register, and the correct result must be in the C5 register. So, first, we note the fact that the C4-2 relay must not be energized, since it contains 0, and that the C4-1 relay must be energized, since it contains 1.
Now the table for negation, with c = -a, is:
| a | c |
| 0 | 0 |
| 1 | 3 |
| 2 | 2 |
| 3 | 1 |
Negation in machine language will be:
| a | c |
| 00 | 00 |
| 01 | 11 |
| 10 | 10 |
| 11 | 01 |