A ''Read-Only'' memory device has been developed which circumvents many of the usual difficulties associated with thin-film devices. The device consists of a relatively thick, uniaxially anisotropic, magnetic film electroplated on a suitable substrate and sandwiched between the conductors of a strip transmission line. A ''thick'' film here is defined as one for which the shape demagnetizing field exceeds the coercive force, thereby causing the film to split into a multi-domain structure. A current applied to the strip line magnetizes the film in the hard direction. Upon removal of the drive current, the shape demagnetizing field and anisotropy field reset the film to its initial multidomain structure. Since the switching and relaxation time of this device will determine the ''ultimate'' cycle time of an array, it is of interest to investigate the switching behavior of thick films. Experimental and theoretical results indicate that both the switching and relaxation of these films take place in time intervals as short as 3 nsec with an applied field of 2 nsec rise and fall time. Individual film elements have been operated with a pulse repetition rate of 20 Mc per sec and higher repetition rates appear possible. © 1963 The American Institute of Physics.