New three-channel open wire carrier telephone system and its application in Norway

Three new systems, working on 3 mm. (4 mm. in one case) open line intermediately loaded have been giving satisfactory service in Norway for a year, and two more systems are being installed. Improved performance was achieved by new features such as stabilised amplifiers, pilot currents in each group, static modulators, and variable line equalisers. The introduction of U-links replacing jacks in the transmission circuits and level measurements have facilitated testing and maintenance. Repeaters were of the 2-wire type, located in the middle of circuits and so kept at a minimum. The description of circuits, equipment, performance, and operation is illustrated by photographs and diagrams.