 for their area. the specification's use by CEPT manufacturers together with its use Band III 46/7 by system operators (Pascoe, 1989). The MPT1327 protocol is short waiting times for communication using a traffic channel. currently used in the 165MHz, 200MHz, 450MHz and 900MHz Dynamic timing is also possible using control channel 'Broadcast' bands. messages which internally set mobile unit call timers dependent upon the traffic density at any particular time. If a user completes 46.4.2 Systems his allocated maximum communication period before reaching the end of the desired message, further traffic channel time is possible Together with public access national systems currently in use by entering the queue again. (Oliver, 1989), these based upon cellular coverage techniques com- Appendix A46.1 gives a selection of available MPT1327 mess- bined with FDMA trunking use, public regional systems are in ages thus indicating the flexibility of the network compared with operation covering major cities. Large private users, e.g. airport alternative systems, Figure 46.5 showing the address codeword structure. authorities (Armstrong, 1989), employ this protocol for efficient usage of a limited number of radio channels on dedicated networks which may also use multi-site operation for area coverage require- ments. The system allows: PREFIX IDENT 1 OTHER FIELDS PARITY 1. Wide area coverage with handoff capability. 2. Individual calls. PARAMETERS 3. Fleet and sub-fleet calls. 4. Inter-fleet calls. 5. PABX interconnection ALOHAS ACKNOWLEDGEMENTS 6. PSTN interconnection. 7. Off-air call set up. REQUESTS/AHOYS 8. Automatic call queuing. 9. Off-air call progress tones from digital signalling received. 10. Emergency and priority call modification. PARAMETERS 11. Status messages. 12. Short and long data messages. 13. Call diversion. SINGLE ADDRESS MESSAGES 14. Queuing of calls for automatic callback. SHORT DATA MESSAGE 15. Indication of calling party identification. 16. Receiver co-channel interference protection. Figure 46.5 Sample M