Table 10
| Switch 1 is closed | Current flows |
|---|---|
| Yes | No |
| No | Yes |
This is like the truth table for “not”; and this circuit is an exact representation of the statement “Switch 1 is not closed.” (Note: These examples are in substantial agreement with Shannon’s paper, although Shannon uses different conventions.)
We see, therefore, that there is a very neat correspondence between the algebra of logic and automatic switching circuits. Thus it happens that:
1. The algebra of logic can be used in the calculation of some electrical circuits.
2. Some electrical circuits can be used in the calculations of the algebra of logic.
This fact is what led to the next step.