. Telephony, Benn. 3. Load sharing, where a number of similar equipments operate in Briley, B.E. (1983) Telephone Switching, Addison Wesley. parallel each carrying a proportion of the traffic. In the event Hills, M.T. and Kano, S. (1976) Programming electronic switching of a fault, the equipment concerned is taken out of service with systems, Peter Peregrinus. the traffic being carried by the remainder at a reduced grade of Hughes, C.J. (1986) Switching - State of the art, British Telecom service. Tech., 4, (1) and (2). Redmill, F.J. and Valdar, A.R. (1990) SPC digital telephone ex- In practice, some combination of these options is often used with changes, Peter Peregrinus. the overall control area being sub-divided dependent on the function Smith, S.F. (1978) Telephony and Telegraphy, 3rd edn, Oxford to be performed. University Press. In the case of traffic dependent equipment such as registers, these Takamura, S. et. al. (1979) Software design for electronic switching are normally dimensioned to carry the predicted busy hour traffic at systems, Peter Peregrinus. the required grade of service in the presence of one or more faults, depending on the predicted fault rate. This page intentionally left blank Telephone exchanges D G Bryan DFH CEng FIEE Telecommunications Consultant (Sections 32.2 - 32.4) Kjell Persson Ericsson Ltd (Sections 32.8 - 32.10) Eur. Ing. S F Smith BSc (Eng) CEng FIEE Northern Telecom (Sections 32.2 - 32.4, 32.11 - 32.19) M Smouts Alcatel Bell Telephone (Sections 32.5 - 32.7) Contents 32.1 Introduction 32/3 32.11 DMS system 32/19 32.2 TXE analogue exchanges 32/3 32.12 The DMS switching network 32/19 32.3 The TXE2 system 32/3 32.13 DMS Peripheral Modules (PM) 32/19 32.4 The TXE4 system 32/4 32.14 DMS-Core 32/22 32.5 System 12 overview 32/7 32.15 DMS-Bus 32/22 32.6 System 12 architecture 32/8 32.16 DMS software 32/23 32.7 System 12 operation and maintenance (O&M) 32/12 32.17 DMS-Link 32/23 32.8 The AXE system concept 32/12 32.18 DMS OA&M 32/23 32.9 AXE implementation 32/14 32.19 Further evoluti