Digital Mobile Radio (DMR) is an open digital radio standard for Professional Mobile Radio (PMR) users & manufacturers. 

The exact technical standards for DMR are specified in the European Telecommunications Standards Institute (ETSI) Standards TS 102 361 parts 1 to 4, the standards are used in products sold in all regions of the world. The applicable ETSI compliance standards are EN 300 113 and EN 300 390. Products built to the DMR standard also comply with the U.S. Federal Communications Commission (FCC) mandates in the United States for the use and certification of 12.5 kHz and 6.25 kHz narrowband technology for systems covered by Part 90 regulations.

The DMR standard operates within the existing channel spacing that is used in land mobile frequency bands (UHF & VHF). Its aim is to specify a non-complex digital system that is low cost and has interoperability across brands, so that purchasers are not locked in to a proprietary solution. DMR provides voice, data, GPS and other services, it is a 2 slot, Time Division Multiple Access (TDMA) system offering voice, data and a range of other features and applications.

In 2005, a Memorandum of Understanding (MOU) was formed between potential DMR suppliers including Tait, ICOM, Motorola, Hytera, Vertex and Kenwood to establish common standards and interoperability. While the DMR standard does not specify the vocoder, MOU members agreed to use the half rate DVSI Advanced Multi-Band Excitation (AMBE) vocoder to ensure interoperability.

In 2009, the MOU members set up the DMR Association to work on interoperability between vendors equipment and to provide information about the DMR standard.

DMR Tier I
DMR Tier I products are for license-free use in the PMR 446MHz band. This part of the standard provides for consumer applications and low-power commercial applications, using a maximum of 0.5 watt RF power. With a limited number of channels and no use of repeaters, no use of telephone interconnects, fixed/integrated antennas, and a talk timer of 180 seconds,

Tier I DMR devices are best suited for personal use, recreation, small retail and other settings that do not require wide area coverage or advanced features.

DMR Tier II
DMR Tier II covers conventional licensed 2 way radio systems, mobiles, base stations and hand portables that are operating in PMR frequency bands from 66-960MHz. The ETSI DMR Tier II standard is targeted at those users who need spectral efficiency, advanced voice features and integrated IP data services in licensed bands for high-power communications. ETSI DMR Tier II specifies two slot TDMA in 12.5 kHz channels.DMR

Tier III
DMR Tier III covers trunking operation in frequency bands 66-960MHz. The Tier III standard specifies two slot TDMA in 12.5kHz channels. Tier III supports voice and short messaging handling similar to MPT-1327 with built-in 128 character status messaging and short messaging with up to 288 bits of data in a variety of formats. It also supports packet data service in a variety of formats, including support for IPv4 and IPv6.