ept where otherwise stated, the In terms of the definitions of time and space switching, given in following description refers to DMS SuperNode. The first gener- Chapter 31, this network can only be described as a time switch. ation (NT-40) is, however, in widespread use so its principal fea- There is no separation of time and space switching functions and the tures are also mentioned. whole network can be regarded as a space switch having time An overview of the DMS system architecture is shown in Figure switches as its crosspoints. Each call is connected via two time 32.12. In the first generation system the speech links are 4 wire switches but the network itself is not divided into separate stages. copper at 2.56Mbit/s in DS30 format comprising 30 digital speech It will be seen that this switching network corresponds to the channels plus parity and supervision. Second generation systems Group Selection stage of Figure 31.10. The line concentration is employ a mixture of DS30 and DS512 optical fibre links (equivalent provided in the relevant Peripheral Module (PM). to sixteen DS30 links each). Similarly, the message links are either DS30 or DS512 but with all channels used for message data. 32.13 DMS Peripheral Modules (PM) 32.12 The DMS switching network A range of different PM is provided to interface the Switching The switching network provides two way digital speech and mess- Network to all external facilities. Four typical ones are shown in aging connections between the Peripheral Modules (PM), interfac- Figure 32.12 and these are described in the following sections. ing both originating and terminating lines and junctions. Security of each network connection is achieved by providing two separate 32.13.1 Line Concentrating Modules (LCM) speech paths (Planes 0 and 1) for every call. The first generation employs a Junctored Network (J-net) com- There is a variety of these PMs which may be housed either at the prising a series of interlinked Network Modules (NM). Each NM Central Office (host site) or at a loc