There are several, what I want to call, Call Types used in DMR. Those include Group Call, Private Call, Alert Call, Emergency Call, and All Call. There may be others, but these are the most common and believe them to be supported across multiple platforms. You might ask why I called them, “call types.” In most DMR radios, during programming, you need to create a “contacts,” list that will allow you to add a contact and what type of contact it is. Typically, you are able to add a contact alias, the contact type, and then it’s ID which must be a decimal number between 0 and 16,776,415. Interestingly enough, Private ID’s mirror this range. So, it is possible to have a private ID and talkgroup ID that are the same. Understand that in the amateur implementation of DMR all users will have a Private ID that is 7 digits in length. Your ID does NOT remove the requirement of saying your callsign. DMR only sends digits. More on the breakdown of DMR ID’s in the amateur implementation later. Remember from above, I mentioned that there is a header and a payload? As it turns out, the call type is included in the header. When you make a group call, the Group Call bit(s) are sent in the header followed by the Contact ID listed for that contact type. This is similar to IP and packet type identification.
The remainder of this section will be dedicated to terminology.
“Group Call” ID's also known as a Talkgroups are used to communicate from one to many. Anyone with the same Group Call or Talkgroup ID can participate in a conversation without restriction. The, “Group Call,” call type is included in the DMR Tier II Standard and is not proprietary meaning, all DMR capable radios shall have this call type as an option.
“Private Call” is used to communicate from one to one or point to point, however, it should not be used for confidential communication in the amateur realm (due to promiscuous mode and SDR devices) but none the less, works great for calls that don’t require the entire groups participation. While all systems support private calls, some support wide area private calls better than others. More on systems later. I know! I know! You want that now, but I am offering a quick background, so you understand why. 😊 The, “Private Call,” call type is included in the DMR Tier II Standard and is not proprietary, meaning all DMR capable radios shall have this call type as an option.
“Alert Call” uses the same concept of Private Calls, and allow the receiving radio to act on that call type. I am remaining vague on purpose, as the reaction of a received, Alert Call is programmable. Typically, it works similarly to “ringing,” the other party. Alert Calls are usually a polite way of starting a Private Call. Usually, us hams, start a QSO by calling the other party via their callsign, so, usually conversations start politely but might not as it’s not a requirement to start a conversation via callsign. Alert Calls work well if your calls go unanswered, usually because the target radios volume has been turned down. The, “Alert Call,” call type is included in the DMR Tier II Standard and is not proprietary, meaning all DMR capable radios shall have this call type as an option.
“Emergency Call.” This one is really cool, but also tricky. Emergency Calls follow the Group Call principal from above. While you aren’t able to select the Emergency Call type from the contacts menu, it is set using an Emergency System in conjunction with a Group Call ID. This doesn’t prevent you from adding a channel to a zone that allows you to use that Emergency Call Group Call ID. This is handy for talking back to a person that activates an Emergency System. Similarly, to Alert Call, Emergency Call can initiate actions both on the sending and receiving radios. Those actions are programmable. This feature is usually used in public safety implementations and is associated to the Orange button on the top of radios. Emergency Calls can be given channel priority when configured properly. Again, emergency stuff is cool, and we will dive into that more later. The, “Emergency Call,” call type is included in the DMR Tier II Standard and is not proprietary, meaning all DMR capable radios shall have this call type as an option.
Finally, “All Call.” All Call follows the Group Call principal from above except it has a set ID and must be specifically enabled. All call is typically NOT supported in the amateur implementation of DMR. All Calls will capture every receiving radio regardless of its talkgroup. All Call can also be allowed to take over calls in progress, this is known as Priority Interrupt. Since it is not support on purpose, I won’t discuss it any further. The, “All Call,” call type is included in the DMR Tier II Standard and is not proprietary, meaning all DMR capable radios shall have this call type as an option.
Hopefully at this point you understand the different call types. This will become critical when building your programing file which is next. Remember that the numbers that are associated to Group Calls and Private Call ID’s can be the same but are different based on the call type. Many radios will not accept duplicate call type ID’s.