In the telecommunication transmission field the word ‘system’ has been widely used for many years when referring in a collective sense to the equipment forming a communication path, usually of multichannel type. The purpose of the paper is to present a broad survey of the systems commonly used in trunk and junction networks, in particular, those in use and being developed in the United Kingdom. Transmission paths, or links, and terminal translating equipment, together with its associated carrier-generation equipment, are treated in separate sections of the paper for convenience of description.Trunk and junction networks, however, rarely consist of multichannel systems alone. For example, in the United Kingdom, as in most other countries, individual audio circuits form a large part of the network; programme and television channels have also to be accommodated. Information regarding equipment for the provision of these facilities is therefore included in the paper.