Interregister multifrequency-code signalling for telephone switching in Europe

The necessity of international agreement on telephone signaling has been felt since 1957 by both administrations and manufactures developing common-control switching systems. The resulting proposal distinguishes two categories in signalling, line and register signals. The article describes the latter type of signalling, using a 2 out of 6 frequency code with all frequencies located in the band 500-2000 c/s. The register signals comprise all signals exchanged between the common control equipments involved in establishing a connection. The various types of signals are discussed and the codes proposed. In a appendix a useful list is taken up of definitions and functions of line signals, as well as definitions of signaling terminology.