Information and Technology has developed rapidly within last decade and now in 21st century the means of communication has reached a level where there is no barrier to it. Now people are free to use individual network lining and can avoid any bad audio quality or fading problems. There are trunking systems that allow better radio frequencies without any line breakage or fading. These systems are comparatively cheaper to older individual lining system.
The digital radio broadcasting technologies now has developed better systems and networks for digital two way radios giving the PMR radio better options to connect and work. These are 2nd generation radio systems and as they are two way, you can both transmit and receive message. These radio systems are most useful for security agencies for individual and mass protection. Police, fireman, military and such security agencies use these types of radio mobile systems.
These systems can be of different types, depending upon their use they can be mobile, stationary base, and walkie talkies. To work these types of radio the networking system needs different levels of support and backup. Such supports should be provided without any interruption and for this a direct satellite network connection is also maintained specially in the case of military and high level security systems. In mountain areas the network gets blocked by different blocks and frequency mix and to solve this problem repeaters are used. A repeater takes the message and retransmits it to higher level so that the message goes without any interruption to long distance.
Digital Mobile Radio (DMR) is an upgraded open digital radio system for Professional Mobile Radio (PMR) and to support them the ETSI (European Telecommunications Standard Institute) made Terrestrial Trunked Radio (TETRA) system. It is a two way receiver and is best for mass security purpose, because with this system one can transfer and receive message from point to point and from point to multipoint and vice-versa. These radios can also be operated hands-free and so can be referred as covert radio.
A digital licence free radio is latest addition to two way radio system that gives you charge-free communication facility. This system is used for private use and they work with the help of repeaters and internet. The only drawback of this radio system is that they work only within few kilometres range that too if the area is clear and viable for PMR and DMR frequencies.
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