What are LMR Systems?
LMR systems enable real-time voice communications between mobile and portable radios over large geographic areas. Two-way radios provide instant group communications for dispatching crews and coordinating field operations without relying on cellular networks that can become overloaded or unavailable during emergencies.
LMR Hardware Components
At the core of every LMR system are the individual radios used out in the field. These can be mobile radios permanently installed in vehicles or portable radios carried by individuals. Radios operate on assigned radio frequencies to communicate with each other or back to a central dispatch location. In larger Land Mobile Radio Systems , radio communications are linked through a network of repeater stations and microwave or fiber optic infrastructure. Repeaters receive radio signals from mobile radios and retransmit them at higher power to extend the range of communications. The repeater infrastructure is monitored and controlled through a central dispatch console that coordinates radio operations.
LMR Communication Methods
There are two primary methods for conducting voice communications on LMR systems - conventional analog and trunked digital. Conventional systems require radios to be manually tuned to dedicated pairs of frequencies, one for transmitting and one for receiving. This limits communications to point-to-point calls between two radios. Trunking systems allow dynamic sharing of a pool of frequencies for more efficient radio usage. Through trunking, groups of radios can participate on calls and dispatchers can select individual radios or entire talkgroups. Digital trunking provides features like data communications, GPS tracking and encryption not available on analog systems.
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