N-GEN Communications Web-based Seminars ©NGCS

Seminar - An Overview of Communications Technologies

Module 9 - Wireless Systems and Technologies                                                                                 Slide 15 of 80                                                                                                    ________________

    Terrestrial Mobile Radio Systems

                                    Paging System

                                    Single Frequency Dispatch System

                                    Two-Frequency Dispatch System

                                    Multi-channel Trunked Radio System

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The mobile communications systems fall into two categories: Commercial Mobile Radio Systems and Private Mobile Radio Systems. Commerce Mobile Radio Systems include all mobile radio systems that offer services for profit and are connected to the Public Switched Telephone Network (PSTN). Public Mobile Radio Systems provide private mobile services. Paging Radio Systems, Taxi Dispatch Systems and Multi-channel Trunked Radio Systems come under the Private Mobile Radio Systems category. 

Paging System - Uses a radio signal to alert or instruct the user.

Dispatch System - A single frequency dispatch system provides a single frequency slot for both a dispatcher and a mobile unit in the field for transmitting and receiving messages. A two-frequency dispatch system provides two frequencies to contact mobile units in the field: one frequency of the pair allows the high power station to transmit and the other frequency allows the lower power mobile units to transmit.

Multi-channel System - These systems, which are operated by very large organizations on a private basis, are designed to provide disciplined access to the channels and to allow messages to share a pool of channels.