A formula is derived for the capacity of a multi‐input, multi‐output linear channel with memory, and with additive Gaussian noise. The formula is justified by a coding theorem and converse. The channel model under consideration can represent multipair telephone cable including the effect of far‐end crosstalk. For such cable under large signal‐to‐noise conditions, we show that channel capacity and cable length are linearly related; for small signal‐to‐noise ratio, capacity and length are logarithmically related. Crosstalk tends to reduce the dependence of capacity on cable length. Moreover, for any channel to which our capacity formula applies, and for large signal‐to‐noise ratio, there is an asymptotic linear relation between capacity and signal‐to‐noise ratio with slope independent of the channel transfer function. For small signal‐to‐noise ratio, capacity and signal‐to‐noise ratio are logarithmically related. Also provided is a numerical evaluation of the channel capacity formula, using measured parameters obtained from an experimental cable.

R. L. Graham and H. O. Pollak recently proposed an addressing scheme to J. R. Pierce's Loop Switching Network—a network system which would exploit the one‐way nature of much data transmission. Our paper provides a generalization of the scheme and proposes a new approach to certain unanswered questions.

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A plan for the introduction of time‐division switching in the intertoll network is outlined. The plan uses the No. 4 ess as the switching vehicle. The plan defines a Switched Digital Network (sdn) which can evolve compatibly with the existing Switched Analog Network (san). The plan introduces 64 kilobits per second time‐division multiplexed pcm as a standard switching signal format in the intertoll network. Facilities utilization, trunk design, timekeeping, and maintenance plans which are required for the new format are presented. Effects on intertoll network evolution, particularly voice performance, are assessed.