The 8.448 Mbit/s PCM transmission over symmetrical twisted twin-pairs in PCM wideband local traffic cables

The results of an 8.44 Mbit/s test transmission over a bundle-shielded cable having five twisted twin pairs per bundle with a conductor cross-section of 0.9 mm are discussed as designated for a PCM wideband local traffic cable. They show that by transmitting with a peak power of 50 mW (the power of a pseudoternary continuous 1 signal) and taking the necessary safety margins for practical operation fully into consideration, a repeater section attenuation of 77 dB can be realized at the half bit frequency of 4.224 Mbit/s. This corresponds to a repeater spacing of 4.3 km. The measured cross-talk values show further that the cable in its existing form is also suitable for the transmission of information at 34 Mbit/s from a PCM tertiary multiplex system with a repeater spacing of 2 km if the transmitting power is increased to 100 mW.