In 1954 the National Company in Malden MA, makers of ham radio equipment, entered the hi-fi market with the Horizon 10 and Horizon 20 amplifiers plus the Criterion AM-FM Binaural tuner and a horn loudspeaker system. The power amplifiers were advertised as having a revolutionary new output circuit employing "Unity Coupling." National literature claimed this feature was exclusive. "With unity coupling in the Horizon 20 and Horizon 10 amplifiers, the output transformer is no longer required to supply coupling between output tubes for distortion cancellation as in normal push-pull circuits. Instead, the transformer supplies only the impedance matching between the tubes and the load, thereby eliminating transformer caused impulse distortion." This was in no way similar to the patented McIntosh Laboratory Unity Coupled circuit and transformer. Gordon Gow decided not to pursue the legal aspect of National's using the unity coupling terminology. The circuitry for the National amplifiers appeared to be poorly designed and constituted no threat to McIntosh. As it turned out, the line of National audio products lasted only a couple of years and were discontinued. The amplifiers reportedly were plagued with problems .