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Circuit Description

This circuit allows changing the polarity of the two outputs; either A0/B1 is connected to A while A1/B0 is connected to B, or A0/B1 is connected to B while A1/B0 is connected to A.

As shown here, the standard logic values are used as inputs to A and B. However, in a more typical scenario, the supply voltage at A and B could (and would) would be different from the relay-coil control supply voltage. One application of this circuit is to change the rotation direction of a DC-motor (e.g. model cars or trains, etc.).