Signalling and control in communication exchanges

The introduction of electronics into telephone exchanges requires changes since electronic devices have different switching characteristics and a much higher switching speed than the metal-contact switches which they supersede. They also offer new opportunities in switching and control for systems of the future. Companion papers examine exchange switches and speech transmission. The present paper generalises the signalling and control aspects of communication exchanges to include all the known forms in one comprehensive statement. Common-processor control and common-channel-junction signalling are of particular interest. The work was part of a study to determine the best kind of electronic exchange for future development. A range of switching units is described of varying degrees of dependence on a central common program-stored processor and their merits for extending existing networks are indicated.