atrix each contain four 16K (in) by 4K (out) time switches combined to form a 16K by 16K matrix. The entire E-net The DMS (Digital Multiplex System) family of digital switches is housed in two cabinets, one for each plane. manufactured by Northern Telecom has variants designed to meet Each shelf of crosspoint cards is controlled by its own processor the requirements of all levels in the network hierarchy (Figure 31.2), communicating with the DMS-Core over a DS512 message link. e.g. DMS-100 for local exchanges of 1000 to 100000 lines, DMS- Referring to Figure 32.13, it can be seen that four incoming 200 for tandem exchanges of up to 60000 trunks or junctions and DS512 pcm signals, or an equivalent number of DS30 streams, are DMS-300 for international gateways up to 27000 trunks. multiplexed into a single 2K (2048 channel) stream by each speech Through the use of highly modular architecture, for hardware and link interface card. The 2K pcm stream from each interface card is software, Centrex, combined local/tandem, mobile telephone, mili- passed to the crosspoint card positioned directly in front of it and tary and PABX (DMS Meridian) versions are also available. This also distributed by a vertical bus (V bus) to the corresponding modular architecture also enables the Intelligent Network applica- crosspoint cards mounted on the other three shelves. Each cross- tions to be integrated with the DMS-100, DMS-200 or DMS-300 point card thus receives four 2K pcm streams, one from its own applications as appropriate. interface and three more from the interface cards above and below The modular architecture permits customisation to meet local on the other three shelves, a total of 8K channels. In addition, the needs and DMS is in service in many countries world-wide includ- vertical buses are mated in odd/even pairs so that each card also ing the USA, Canada, Europe and Japan. In the U.K., DMS ex- receives a further 8K channels from the adjacent mated bus. This changes form the basis of the Mercury network and provide gives