Application of single channel carrier to existing loaded cables in Switzerland

Describes a system in which a second channel is superposed on extra light phantom circuits having a cut-off frequency 7000 ~. As these circuits were designed for voice frequency working only, their possible use at carrier frequencies involving probabilities of noise and crosstalk required investigation. Tests were carried out on a 360 km. circuit from Berne made up of six repeater sections and containing cables manufactured at widely different times. The tests showed that single channel circuits of good quality could be obtained. The paper details the tests, the circuits employed, and the results obtained.