AIS-based location aid device numbering
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Contents
Overview
In accordance with Liaison Statements issued by ITU-R Study Group 5 in 2008 and 2011, CIRM has the responsibility for issuing Manufacturer ID numbers to companies producing AIS-based location aid devices, including AIS-SART, Man Overboard, and EPIRB-AIS.
CIRM maintains a table of numbers and to whom they are issued, which is available on the CIRM website.
Numbering scheme
In order for these devices to be received on a standard AIS receiver, they must transmit a 9-digit number. This number is not an MMSI (MMSIs are issued by administrations and recorded in databases such as the ITU MARS).
History of the numbering scheme
It would have been possible to have used a MMSI with an AIS-SART. MMSIs are issued by administrations and recorded in databases such as the ITU MARS. However since the AIS-SART is an equivalent to the radar SART and the radar SART does not transmit any information about its identity it was considered that the AIS-SART did not need to transmit a MMSI. So any 9-digit number could be suitable for an AIS-SART as long as it could not be confused with a MMSI.
Another consideration is there are likely to be more than one AIS-SART operating in the same area at the same time. SOLAS requires ships to carry two SARTs and RoRos to carry a SART in every fourth liferaft. These should ideally all have different numbers, otherwise the receiving AIS equipment will be jumping between different positions.
The structure on page 8 was thought to minimise the probability of the same number turning up on AIS-SARTs carried on the same ship. The industry asked for this structure so that they could programme in the number at manufacturing time and there was no need for any interface to subsequently change it.
Structure of the 9-digit number
The first three digits of the number identify the type of device (97X prefix). The fourth and fifth digits together identify the manufacturer that produced the device (the “Manufacturer ID”). The final four digits identify the individual unit number of the device.
The 2011 liaison statement indicates that the preamble 97X should be used as follows:
- 970 AIS-SART devices
- 972 Man Overboard devices
- 974 EPIRB-AIS devices
Each number allows for 9999 units to be manufactured to that identity, however ITU advises that when this number is reached the manufacturer should should revert to 0000 and begin numbering again.
How CIRM allocates IDs
CIRM’s original practice was to issue multiple allocations to each manufacturer applying for an ID, because at the time there was a concern that manufacturers would run out of unit numbers for their devices. ITU subsequently decided that the unit numbering scheme could begin again at 0000 once 9999 was reached, in the recognition that the industry was in danger of running out of manufacturer IDs.
CIRM accordingly changed its policy and started issuing one ID per manufacturer. However by this stage a large number of IDs had already been issued to manufacturers (some of which were later reclaimed).
On registration of numbers
AIS-SART was not originally intended as a distress alerting device but as a location aid, and so the idea behind numbering of AIS location-aid devices was that such devices would not be registered. During development of the AIS-SART standard, it was decided not to add the ability to program a number into it - so the procedure of using a manufacturer number installed at the manufacturing stage was agreed with ITU and IMO.
There is no requirement for the manufacturer to maintain a database of device identifiers. In fact manufacturers typically say that they have no idea who the ultimate customer is of their device. The best they generally know is the agent to whom they sold it.
