Understanding DMR (Digital Mobile Radio)

Digital Mobile Radio or DMR for short is an open standard or protocol for digital mobile radios defined by the European Telecommunications Standards Institute (ETSI) and are used in commercial products around the world. DMR was designed to allow for more bandwidth on a particular frequency. Or more plainly, to allow for more transmissions in a smaller space. 

You may have seen DMR referred to as DMR I, II or III.  

DMR I - Non-licensed conventional

DMR II - Licensed conventional

DMR III - trunking

DMR is a TDMA mode (Time Division Multiple Access) which means that it allows several users to share the same frequency channel by dividing that signal into different time slots. Each frequency has a slot 1 or slot 2 and each slot can be used by different users.  Each user transmits in rapid succession using their own time slot. This allows multiple stations to use the same frequency channel while only using part of the channel's capacity.  

All DMR frequencies use Color Codes from 0-15 and all frequencies for a site will have the same color code. Each transmitter can have only one color code. Con+ and Cap+ systems can use different color codes on different frequencies. 

There are 6 different "flavors" of DMR. TalkGroupIDS (TGID) are used with all 6 flavors of DMR and encryption or scambling may also be used. 

The  flavors of DMR are:

  • Conventional Digital Mobile Radio (DMR)
  • Internet Protocol Site Connect (DMR)
  • Capacity Plus (Cap+)
  • Linked Capacity Plus - trunked multi-site muli-channel configuration of MotoTRBO which combines both Capacity Plus and IP Site Connect configurations.
  • Capacity Max
  • Connect Plus (Con+)

Need a recap?

  • DMR has 3 tiers of operation - Tier I for non-licensed conventional, Tier II for licensed conventional and Tier III for trunking
  • All types of DMR get one system type - DMR
  • Each DMR frequency uses a Color Code
  • If you are entering conventional DMR channels as a trunked system each TGID must be unique within that system. 

So what does this mean to me?
So basically what you need to know is that the WS1080/88 and WS1095/98 scanners are upgradeable to receive DMR and the TRX-1 and TRX-2 will receive DMR out of box. Each flavor or DMR uses the time slots slightly different and encryption can be used in DMR. Unfortunately some systems are encrypted and no scanner will ever be able to monitor encrypted signals.