n the UK or Okumura, Y. et. al. (1968) Field strength and its variability in v.h.f. the US. and u.h.f. land mobile radio service, Review of the Electrical The ground transmitter frequency used is 931MHz and this fre- Communications Laboratory, 16, (9 and 10), September/Oc- quency has also been allocated or reserved in Canada, Singapore, tober. Malaysia, Shanghai, Bolivia, Brazil, Uruguay, Ecuador, Peru, Sri Sandvos, J.L. (1982) A comparison of binary paging codes, IEEE Lanka and Venezuela. Vehic. Tech. Conference, May. Tridgell, R.H. (1982) The CCIR radio paging code no. 1, a new world standard, IEEE Vehic. Tech. Soc. Conference, May. 45.12 Bibliography Tridgell, R.H. and Denman, D. (1984) Experience of CCIR radio- paging code no. 1 (POCSAG) for message display paging, IEE BT (1980) A standard code for radio paging, report of the Post 1984 Conference on Mobile Radio Systems, September. Office Code Standardisation Advisory Group (POCSAG), June 1978 and November 1980. PMR and trunked radio systems C Lorek BSc (Hons) AMIEE South Midlands Communications Ltd Contents Private Mobile Radio 46/3 PMR systems 46/3 Trunked mobile radio 46/5 Band III 46/6 The use of troposcatter 46/8 Transmission standards 46/8 Analogue signalling 46/9 Data transmission 46/10 Applications 46/13 46.10 Appendix 46.1 46/13 46.11 References 46/13 This page intentionally left blank Private Mobile Radio 46/3 Private Mobile Radio 46.1.2.3 Battery requirements for portable equipment Private Mobile radio, or PMR, has developed substantially over the In the case of portable equipment, the rechargeable battery source years, from simplex AM communication on a single channel emplo- is often the limit in the equipment's overall size and hence port- ying crystal controlled equipment, to that of today's multiple chan- ability. Developments in reducing portable equipment size are nel systems employing synthesised transceivers operating under likely to concentrate in this area. Nickel hydrogen cells are being microprocessor control, often with intelligent cha