The XNOR Gate is a Redstone circuit block added by the Redpower2 mod. As the name suggests, it acts like a simple XNOR gate for redstone. The XNOR Gate has 2 Inputs and 1 Ouput. The Output is on when both Input states are the same. The output is off when both Input states are different. This also means when any Input state is changed, the Output state will change too. The image on the right shows the 2 Inputs that are linked together. Similar gates are the OR Gate, the NOR Gate and the XOR Gate.
The XNOR Gate can be used for light switches, where both levers control the same lightsource. The use of light switches is similar with the XOR Gate. When using a XNOR Gate, using an Invertor is no longer necessary in combination with an XOR Gate. It will give the same outcome, however, the XNOR Gate gives the advantage that it needs little space, less material and is less complicated.