32.7.1 of disc systems. The Network Service Centre 6. The maintenance software handles the processing of any ex- change hardware and software faults to ensure the continuity of It can be directly integrated with a System 12 exchange or used in a call handling operations. standalone mode. It is constructed from standard System 12 mo- 7. The status and alarm software controls the status condition of dules, CCITT No.7 signalling modules, and X.25 packet interface terminal processors, records and displays alarm situations. modules. Generally a network service centre is connected to a 8. The Clock and Tone, calendar software contains the Clock and number of exchanges via CCITT No.7 links. Tone device handler software, the associated diagnostic and routine tests, calendar scheduler handler and interactive control 32.7.2 Advanced Terminal for Operation and software. Maintenance (ATOM) 9. The Line and Trunk Testing software gives test and mainten- ance facilities for subscriber and trunk lines. A user friendly man machine interface has been provided by means 10. The Call Handling and Facilities software interfaces with the of PC programmes called ATOM. other exchange to control the set up and connection of a call, This terminal provides functional screens representing parts of the through the exchange, to its destination. system functions like e.g. system diagram, trunking diagram, floor 11. The Signalling handling software provides an interface be- plan etc. which allow by clicking of the mouse to instruct the system tween the signalling systems and the call handling and facilities which function has to be performed. software. Also for an easier overview of the exchange performance, post 12. The Telephonic Device and Signalling Adaption software pro- processing function are performed to display information like stat- vides the interface between the telephonic devices and the istics, received error reports, alarms etc. (see Figure 32.5). Signalling Handling software. 13. The Call Services software supports the Call Handl