Abstract: A group delay equaliser for a repeater in a waveguide communication system uses a magnetostatic wave delay line as a dispersive element to compensate for inherent dispersion in the waveguide. The delay line uses a thin ferrimagnetic film in which a propagation path is defined which is biased by a uniform adjustable magnetic field which is established to provide an adjustable dispersion characteristic. The film has associated with it means for preventing reflections of magnetostatic waves propagated beyond the ends of the propagation path. A substantially linear propagation delay with frequency is achieved over a bandwidth of 500 MHz. at a centre frequency of 1.5 GHz.