L3 Technologies AISA1 ユーザーズマニュアル

The Assigned and Polled operational modes are activated through a DSC message
transmitted by the competent authority.  In order to provide for this, the ProTec AIS
contains a dedicated DSC receiver that is tuned to channel 70.   DSC messages
originating from shore stations of competent authorities will define regional AIS fre-
quencies, regions of coverage, required transmission schedule and/or interrogation
request.  The ProTec AIS will respond back to such DSC interrogations on the fre-
quency specified in a manner such that it does not interfere with the TDMA transmis-
sions by interleaving the transmission between TDMA transmissions.  The DSC re-
sponse will be made after a random delay of 0 - 20 secs provided the signaling
channel is clear and the TDMA transmissions are not interrupted.

A Class A AIS unit broadcasts the following information every 2 to 10 seconds while
underway, and every 3 minutes while at anchor at a power level of 12.5 watts. The
information broadcast includes:

MMSI number - unique referenceable identification.

Navigation status

Speed over ground - 1/10 knot resolution.

Position accuracy - differential GPS.

Longitude - to 1/10000 minute and Latitude - to 1/10000 minute.

Course over ground - relative to true north to 1/10th degree.

True Heading - 0 to 359 degrees derived from heading sensor.

Time stamp - The universal time to nearest second that this information

was generated.

In addition, the Class A AIS unit broadcasts the following information every 6 
minutes:

MMSI number - same unique identification used above, links the data

above to described vessel.

IMO number - unique referenceable identification (related to ship’s

construction).

Radio call sign - international call sign assigned to vessel, often used on

voice radio.

Name - Name of ship, 20 characters are provided.

Type of ship/cargo - there is a table of possibilities that are available.