sentences:  During the period when Type N-1 was in widespread use, Lenkurt Corporation, owned and controlled by General Telephone, fielded a variant competitor, the Type BN.BN used the same pairs and repeaters as did the Bell N-CXR, but used four channel "groups," lower single-sideband heterodyning, and 24 channels per carrier, as later seen on Western Electric's Type N-3.Type BN was used at times by Bell Operating Companies after the 1956 Hush-a-phone Decision of the US Supreme Court, a landmark case which challenged AT&T's "benign monopoly" of US telephone equipment industry.