Converting a Flat Number to a DMR ID

MOTOTRBO Capacity Max Radios and Infrastructure uses the DMR Air Interface as described in ETSI TS 102 361-1 (v2.5.1) Annex A*. This basically means that if the user makes a call to Talkgroup 123, their radio actually sends 123.

At least one vendor has chosen to use the numbering scheme defined in ETSI TS 102-361-2 (v2.4.1) Annex C.2.1.1*. This numbering scheme applies to Talkgroup IDs. Using this scheme, if the user makes a call to Talkgroup 111, the radio actually sends out 133. This can be challenging when provisioning MOTOTRBO (or any other make of) radios to work on a DMR Tier 3 system from this vendor.

To convert a so-called Flat talkgroup number into a DMR AI Talkgroup ID, use the following method:

Write the "flat" number down as a seven-digit number. So, for example, 111 would be written as 0000111 and 56677 would be written down as 0056677. Write this seven-digit number down vertically with the most significant digit at the top, like so:

0

0

0

0

1

1

1

Then multiply each digit separately by 1464100; 146410; 14641; 1331; 121; 11 and 1, starting from the most significant digit (decimal big endian) to the least significant digit as shown below. So to convert 0000111, you would do the following:

0 × 1464100 = 0

0 × 146410 = 0

0 × 14641 = 0

0 × 1331 = 0

1 × 121 = 121

1 × 11 = 11

1 × 1 = 1

Add all the products and you'll get 133.

And to convert 0056677:

0 × 1464100 = 0

0 × 146410 = 0

5 × 14641 = c73205

6 × 1331 = 7986

6 × 121 = 726

7 × 11 = 77

7 × 1 = 7

Add all the products and you get 82001.

As a further example, to convert 1221343 you would do the following:

1 × 1464100 = 1464100

2 × 146410 = 292820

2 × 14641 = 29282

1 × 1331 = 1331

3 × 121 = 363

4 × 11 = 44

3 × 1 = 3

Adding the above products gives 1787943. So when adding talkgroup 1221343 to a MOTOTRBO radio, you would enter 1787943 into Radio Management.

If you want to use Microsoft Excel (or whichever spreadsheet application you choose), try this formula:

=IF((LEN(A1)=7);(MID(A1;1;1)*1464100)+(MID(A1;2;1)*146410)+(MID(A1;3;1)*14641)+(MID(A1;4;1)*1331)+(MID(A1;5;1)*121)+(MID(A1;6;1)*11)+(MID(A1;7;1)*1);0)

The Flat ID would, in this case, go into cell A1. This cell (A1) must be formatted to present the entered number as seven digits (i.e. 0000000). The LEN statement makes sure the entered number is indeed seven-digits long otherwise the result will be wrong.

If however, the radio is using MPT1343 dialing scheme, read this post.

* ETSI TS 102 361-1 (v2.5.1) Annex A is normative which means that vendors have to comply with it in order to say their device is DMR. ETSI TS 102-361-2 (v2.4.1) Annex C is informative which means vendors don't need to implement this at all.