Abstract :
It is shown that the probability distribution of pulse distortion magnitudes in a multi-channel pulse-transmission system forms an important consideration in the design of such systems, and if properly taken into account may form the basis of considerable economies in design. An analysis of inter-channel interference distortion is given, and it is shown how the probability distribution may be determined for the type of system likely to be encountered in practice, i.e. with interference of equal amplitudes from two adjacent channels on each of two or more links in tandem. It is shown that on a typical multi-channel v.f. telegraph system with two links in tandem, only about one pulse in a thousand is distorted more than half the maximum amount, and only one in six hundred thousand more than three-quarters the maximum amount. In the case of a single-link multi-channel v.f. telephone dialling system, only about one in eighty thousand pulses is distorted more than half the maximum amount and only one in forty million more than three-quarters the maximum; on two links in tandem, only about one pulse in ten thousand is distorted more than one-quarter of the maximum amount, and only one in a million more than one-third of the maximum. It is quite evident, therefore, that the maximum distortion need not be the basis of design, but instead some smaller figure, say one-quarter to three-quarters of the maximum.
