Land Mobile Radio

Land mobile radio system (LMRS), also called public land mobile radio or private land mobile radio, is a wireless communications system intended for use by terrestrial users in vehicles (mobiles) or on foot (portables). Examples are two way radios in vehicles. Such systems are used by emergency first responder organizations such as police, fire, and ambulance services, public works organizations, dispatched services such as taxis, or companies with large vehicle fleets or numerous field staff. Such a system can be independent, but often can be connected to other fixed systems such as the public switched telephone network (PSTN) or cellular networks.

The land mobile radio system is also the United States Department of Defense's new state-of-the-art communication system. Government contractors, such as Cassidian Communications, Relm Wireless Corporation, Harris Corporation, Kenwood Communications, Motorola Solutions, Raytheon, Thales, and Tyco Electronics, provide the latest in LMRS technology to the government and military.

Many businesses and industries throughout the world use LMR as their primary means of communication, especially from a fixed location to mobile users (i.e. from a base site to a fleet of mobiles). Commercial LMR Radios are typically available in two VHF and the UHF frequency bands. 30−50 MHz (sometimes called "Low VHF Band" or "Low Band"), 150−172 MHz (sometimes called "High VHF Band" or "High Band"), 450−470 MHz (called, simply, "UHF" for "Ultra High Frequencies", a term created in the 1950s). Many larger populated areas have additional UHF frequencies from 470−490 MHz, and 490−512 MHz. Low band has longer range capability, but requires mobile antennas as long as nine feet (2.7 m) tall. VHF bands works well in outdoor environments, over bodies of water, and many other applications. UHF bands typically perform better in urban environments and with penetrating obstacles such as buildings. There are also frequencies in the 800 and 900 MHz range available. Commercial, public safety and government users are required to obtain U.S. Federal Communications Commission licensing in the United States and must follow Government law.

...
Wikipedia