DMR

See this YouTube video link below which gives a rundown of how the DMR system works.
Thanks to Kevin KB9RLW The old Tech Guy for this video.
DMR Discussion on how it works

What is DMR

DMR stands for Digital Mobile Radio.
It was created by European Telecommunications Standard Institute (ETSI).
It uses Time Division Multiple Access (TDMA) technology to enable two independent voice paths all within a single 12.5kHz channel. Compared to the older analog radios, DMR offers advantages such as a higher voice quality, richer functionality and greater spectrum efficiency.
Used on the VHF and UHF bands and started by DMR-MARC around 2010.
As it is globally adopted, digital radio standards, DMR's is tiered architecture and called, Tier I, II and III, which provides targeted solutions for different application scenarios. The DMR follows a three-tier platform:

• Tier I: License-free equipment e.g. PRS, power ≤0.5W, no repeater functionality. Suitable for personal recreational use.
• Tier II: Licensed conventional communication, supports repeaters and IP data services, the mainstream choice for amateur radio use.
• Tier III: Trunking systems. Primarily this is used for professional, dispatch scenarios.

Coordinated DMR Identification Numbers are assigned and managed by RadioID Inc. Their coordinated database can be uploaded to DMR radios in order to display the name, call sign, and location of other operators.
Internet-linked systems allow users to communicate with other users all around the world via connected repeaters, or DMR "hotspots" These are often based using a raspberry pi. There are currently more than 5,500 repeaters and 16,000 hotspots linked to the BrandMeister system worldwide.
The low cost and increasing availability of internet-linked systems has led to a rise in DMR use on the amateur radio bands. Some DMR hotspots, often those running the Pi-Star or WPSD software, allow users to connect to multiple internet-linked DMR networks at the same time.

Breakdown

• DMR ID – Which is your "digital ID": it is made up of a 7-digit unique identifier, which you need to gain access to the network. Apply for free, click on the link to Radio ID’s website.
  Radio ID
  


• Time Slot - Dual-lane communication: Using TDMA, it divides a 12.5kHz channel into Slot 1 and Slot 2 for two independent communication paths, like two stations talking at the same time and don't interfere with each other.


• Colour Code – this is like the digital equivalent of CTCSS tones. Ranges from 1-15, and used to distinguish between the different systems, all on the same frequency. The colour must match the same repeater settings to communicate.


• Talkgroup – These are the chat rooms which can be your local or worldwide group. These user group calls are pre-programmed that allow simultaneous calling with a single button press which can support instant group calls from dispatched applications for multiple users.


• BrandMeister– This is one of the world's largest DMR network system. It connects repeaters worldwide into a unified network.