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During recent years, of the problems which have presented themselves to engineers on electrical transmission and distribution systems, those of voltage and switch control have probably been the most interesting. Supply systems may be classified as either rural or urban; the latter type is that on which the experience and particulars for the preparation of this paper have been obtained. It is believed that the city of Manchester is the first area to have complete automatic voltage regulation, and also supervisory control for its main substations. Some particulars of the investigations made, equipment installed, and results obtained, are given, together with a brief outline of the growth of systems, and reasons why better control of voltage is necessary. It is claimed that, by a careful application of automatically-controlled compensated voltage-regulators in main substations, the voltage on distribution networks may be economically maintained within the permissible limits of Â±4 per cent; and that, generally, the voltage variation at individual services may be kept within 4 per cent overall. At the same time, the fluctuations at the secondary terminals of high-voltage power consumers' transformers may be maintained within the limits for low-voltage distribution. Abnormal cases will, however, occur and will require special treatment. The limitation of voltage variation to such a small amount possesses definite technical, economic, and psychological value; and available records over a short period suggest that it also results in increased sales of energy. The value of supervisory control is referred to, and one system is described in some detail.