# Petherick code

The Petherick code is a one-step code, like the Gray code or the Glixon code. The Petherick code differs from the above codes in that it does not use the two code words

0000 and 1111, the same is true for the Gray excess code and the O'Brien code.

The code words of the Petherick code are constructed in such a way that the 9's complement is obtained by inverting the most significant bit (MSB). The mathematical complementfacilitates the representation and calculation with negative numbers and the subtraction of numbers. The Petherick code is used in control technology, for example in angle encoders.