The N2 Carrier Terminal -- Circuit Design

During the early 1950's there began to appear a series of carrier telephone systems intended for short-haul use. The first of these was N l , 1 a 12-channel double-sicleband system for single-cable application. The rapid growth of the telephone plant resulted in large demands for these systems. Advances in the art, particularly those associated with the transistor and other solid-state devices, have made possible an improved design of the N system terminal. The circuits used in the new N2 terminal arc described in this paper. The N2 carrier system functions primarily as a connecting link over moderate distances for four-wire voice-frequency circuits. Basic considerations affecting the system layout are covered in a companion paper. 2 The principal features of the earlier Nl system are retained, including the use of compandors, double-sideband modulation and detection, and gain regulation on both a group and an individual channel basis, as well as provision for slope and flat gain adjustment of 761