ain a charging facility to recharge pagers overnight. module on its bus. The remote link controller allows the system data bus to be Operators can send paging calls and enter and update information extended via any RS232c compatible link. For examples modems by means of small local control units, or larger alpha numeric and telephone lines, KiloStream, MegaStream, or data networks can control units and, if on a large site connected by private wire, all be used to carry the link. operation can also be made by remote control unit via a gateway The system has a large data base containing user, remote contact module. interface and team records. This provides comprehensive data pro- The telephone interface units shown are via interface cards, which cessing and organising functions for these records and the memory provide a direct hard wired link between the paging system and PTT is protected against power supply failure by battery backup. The or other approved private lines, selector level circuits, extension memory allows all records to be sent to a dedicated printer for a hard circuits or tie line type circuits. The cards provide the correct copy. electrical signal conditioning and safety requirements of such con- Through this unit, a pager's identity can be transferred to another nections. pager, if the first pager is withdrawn from service for repair. If a user 45/8 Radio paging is going off site, for example, or if the user is on holiday, he can have code formats, both analogue and digital, can be found on large on his calls transferred to another user's pager, by entering the relevant site systems. data and identity into the data base. New teams of users can be constructed readily by the operator, for group calling purposes. 45.6.2 Transmitter synchronisation Figure 45.2 shows paging transmitters from each of the two sites and also a base receiver, to enable talkback paging to be used. On large sites, or in areas of difficult propagation, it is often necessary to use multiple transmitters to give adequate radio 