The 'shift and add' property of maximum length pseudorandom binary sequences (m-sequences) is a well known property in which the modulo-two addition of any two identical m-sequences with different phases generates another identical m-sequence, but with another phase. The parameters of the 'shift and add' property of an m-sequence are derived from the Galois field. Its application to channel characterisation of digital magnetic recording including nonlinearities is described. Finally, all the 63-bit and 127-bit m-sequences with parameters which describe the nonlinearities of the recording channel are tabulated.
