Private Mobile Radio (PMR) is sometimes called Professional Mobile Radio and it was developed for business users who need to keep in contact over relatively short distances with a central base station or repeater. A typical example is a taxi company. PMR is also widely used by emergency services. PMR networks consist of one or more repeater stations, one or more base stations and a number of mobile terminals. Such a system serves a closed user group and that is normally owned and operated by the same organization as its users.
From their early designs, PMR systems have developed into 'trunked' systems, the most notable of which is TETRA, Terrestrial Trunked Radio. Trunking is a technique where the resources of the communications network are shared, thus providing both flexibility and economy in the allocation of network resources. Typically, a communication channel is allocated for the duration of a call and then automatically released to allow it to be used for another call , perhaps between different users on the same system. The technique also enables multiple base stations to be connected and to provide coverage across a wider area than with a single base station.
PMR systems generally provide facilities for closed user groups , group call and push-to-talk , and have call set-up times which are generally short compared with cellular systems . Many PMR systems allow Direct Mode Operation in which terminals can communicate with one another directly when they are out of the coverage area of a network.
Main Frequency Registry (MFR)
(a). High Frequency (HF)
(b) Very High Frequency (VHF)
(c) Ultra High Frequency (UHF)
In the above frequency ranges for the Private Mobile Radio, the following types of radio stations can
(a) Repeater radio stations
(b) Base radio stations
(c) Mobile Stations (Vehicle mounted)
(d) Portable or Handheld radio stations
These radios can be operated in two ways.
(a) Semi-duplex operation
(operation through the transmitter at two frequencies)
(b) Simplex operation (operation at one frequency)
How to apply for Frequency Licence for PMR system?
Any person or organization needs to operate PMR communication network, it is necessary to obtain a Frequency Licence from Telecommunications Regulatory Commission of Sri Lanka. The request should be complied with the Special instructions and General Instructions attached to the Application Forms.