DMR, or Digital Mobile Radio, is a digital radio standard used for professional mobile radio communications. It enables efficient voice and data transmission, making it popular among emergency services, transportation, and other industries. DMR operates in various frequency bands and supports multiple users on the same channel through time division multiple access (TDMA) technology. The DMR standard is divided into three tiers: Tier I for unlicensed use, Tier II for licensed conventional systems, and Tier III for trunked systems. Each tier offers different features and capabilities, allowing organizations to choose the best option for their communication needs.