Carrier Transmission on Voice Loaded Loops

A new telephone line loading scheme is reported that permits application of subscriber carrier systems to voice loaded cable pairs with practically no degradation to either voice or carrier transmission. This scheme, termed super-loading, makes use of a bifilar wound toroidal inductor having both windings center tapped, with an LC network joining the center taps. This arrangement produces a device that acts as a one-to-one transformer at frequencies where the LC network presents a low impedance and a series inductor when the network impedance is high. Data are presented comparing the transmission characteristics of nonloaded, nominally loaded, and super-loaded cable pairs at voice and carrier frequencies.