Transmission properties of polyethylene-insulated telephone cables at voice and carrier frequencies

In the last few years, amplitudemodulated carrier telephone systems up to about 250 kc have been routed over polyethylene toll cables and frequencymodulated carrier telephone systems up to about 350 kc have been routed over entrance cable for open-wire circuits. Trunk cable carrier systems with top frequencies of 400 kc or more are under development. Study is being given to pulse-code-modulated cable carrier systems with top frequencies of a megacycle or more. The problems of crosstalk control and noise shielding at carrier frequencies have, therefore, become of prime importance.