Developments in carrier telegraph transmission in Australia

An account is given of the development of carrier telegraph transmission in Australia, from 1927 to the present time. The first system, a Western Electric Type B, of 10 channels, was installed in 1927 between Melbourne and Sydney and was gradually extended to other links. The first voice-frequency carrier system was installed in 1935 and later developments have mainly comprised systems of this type. Supply difficulties due to the war led to production of the necessary equipment, required to meet the heavy demands of the Services, in Australia. A general description is given of the Type B system and also of the main features of the 18- and 9-channel. v.f. systems, including filters, compensating networks, harmonic oscillators and supply units.