Specifications

5.2.6

AIS 6 - REGIONAL AREAS

Two VHF and one DSC receiver channels have been designated for AIS use worldwide.

These frequencies are:

• AIS 1 (Channel 87B, 161.975 MHz, (2087)

• AIS 2 (Channel 88B, 162.025 MHz, (2088)

• DSC (Channel 70, 156.525 MHz)

Under normal masterless operation, the MX535B AIS transponder operates autonomously with other

ships or AIS base stations using the AIS1 & 2 frequencies. When entering areas controlled by a

competent authority (i.e. Coast Guard) under Vehicle Tracking System (VTS) rules, the MX535B AIS

transponder can be polled and controlled by the VTS station. In this situation, data communication

between ship-to-ship and ship-to-shore stations is done through the DSC frequency (channel 70). All

VTS related activities are happening without any user intervention.

The controlling VTS base station schedules all ship’s data transmission and provides the regional

parameters shown in AIS 6 display, such as:

• Operating frequency, bandwidth and mode of Channel A & B receivers

• Northeast and Southwest corner coordinates of the region

• Zone size

• Date and time tag

These parameters are stored in the memory bank of the AIS transponder and can be displayed in the

MX420/AIS CDU. Up to eight regions can be stored by the transponder. The AIS constantly checks

the stored region boundaries and compares it to its own position. If the distance to the region

boundaries is greater than 500 miles from its own position or the time tag was older than five weeks,

those stored regions will be erased from memory.

The operator (administrator) has the option to do a full or partial editing of the regional parameters

when needed. The conditions below have to be observed when editing:

• Use the correct channel numbers (see table A-1 or in the AIS card)

• Latitude difference should be no less that 20 NM or larger than 200 NM

• Longitude difference should be no less than 20 NM or larger than 200 NM

• The zone size should be no less than 1 square mile or larger than 8 square miles

• Distance to the zone is less than 500 NM from you current position

Manual entries violating any of the above conditions will be rejected by the AIS transponder

without notifying the operator. If the region memory is full, the oldest regional memory will be

replaced by a newly accepted one.