By combining the basic logic circuits described so far, a circuit with a specific function can be configured.
Here, we will explain about the XOR (*) circuit used for a comparator that checks for the data mismatch and the adder.
The switch in the figure defines the pressed state as "ON" and the pulled state as "OFF".
When switch A is "ON", the upper circuit is connected and the lower circuit is disconnected.
On the contrary, when it is "OFF", the lower circuit is connected and the upper circuit is disconnected.
When switch B is "ON", the upper circuit is disconnected and the lower circuit is connected.
On the contrary, when it is "OFF", the lower circuit is disconnected and the upper circuit is connected.
If the A and B switches are combined as shown in the figure, no current will flow and the light bulb will not turn on, when both A and B are "ON" or both are "OFF".
The circuit is connected and the light bulb is turned on only when A and B do not match, such as A is “ON” and B is “OFF”.
As shown in the truth table, the output Y is 1 when 1 is input to either of A and B.
The schematic can be expressed by the MIL symbol as shown in the right figure.
* Abbreviation for Exclusive OR