Marine Systems
Aviation Recorders
Page 1–10
Initial Issue
165M0601-00
Feb. 01/05
1.3.6.
Operational Modes
The ProTec AIS is designed to operate in each of three modes: Autonomous and
Continuous, Assigned and Polled which are defined below.
1.3.6.1
Autonomous and Continuous
This is the default mode. The ProTec AIS will determine its own schedule for trans-
mission of position and identification and will automatically resolve scheduling con-
flicts with other stations using the Self Organized Time Division Multiple Access
(SOTDMA) methodology.
1.3.6.2
Assigned
The ProTec will automatically switch to assigned mode when it is commanded by a
competent authority, such as a base or repeater station, to transmit on a specific
transmission schedule. In this mode, the ProTec allocates the defined slots and be-
gins transmitting on these slots. It will continue to transmit in these slots with a zero
slot time-out and a zero slot offset, until those slots have been removed from the
transmission schedule. The assigned slots use the SOTDMA access scheme, with
the time-out value set to the assigned slot time-out. The assignment terminates
when the slot time-out reaches zero of any assigned slot, and the ProTec returns to
autonomous and continuous mode.
1.3.6.3
Polled
The ProTec AIS will transmit a response to DSC interrogation messages from a ship
or competent authority and respond back on the same channel without interfering
with either of the other two modes. When an automatic response is required, trans-
mitted responses will be made on channel 70 unless the unit is instructed to transmit
on another channel. The ProTec is inhibited from transmitting on the AIS 1 and AIS
2 channels. If and when frequency channels other than channel 70 are used for
DSC transmissions, the receive capability of TDMA operations should not be
impaired more than it would be if all DSC messages were transmitted on channel
70.
1.3.6.4
Initialization
The ProTec AIS will enter into an Initialization mode at Power-Up during which it will
monitor the TDMA channels for one minute. During this initialization period, a dy-
namic directory of all users in the system will be created which includes user IDs,
slot assignments, positions, and other transmitted data. After this initialization period
of 1 minute, the ProTec will enter the required operational mode and begin transmis-
sion of the AIS data on the required schedule.
