SRT AIS, Installation And Operation Manual

Page: 72 / 92

Technical Information
Page 70
for 30 seconds, the port shall be deselected as a COG+SOG source, and a
new source selected as described above.
6.11.3 Heading Priority Scheme
Heading shall be taken from the highest priority sensor reporting any one of:
• HDT
• THS
HDT and THS are only processed if they are from the currently selected Head-
ing source. When no heading has been received on the selected port for 30
seconds, the port shall be deselected as a heading source, and a new source
selected as described above
6.11.4 Rate of Turn Priority Scheme
Rate-of-Turn shall be taken from the highest priority sensor reporting ROT.
ROT shall only be processed if they are from the currently selected Rate-of-
Turn source. When no Rate-of-Turn has been received on the selected port
for 30 seconds, the port shall be deselected as a Rate-of-Turn source, and a
new source selected as described above.
6.12 Compatibility Mode
Some devices require the use of Compatibility Mode for correct operation.
When operating in the standard mode the fix quality flag indicates the type of
GNSS position that is being reported. In compatibility mode, the fix quality re-
ported will either be No GNSS or GNSS.
On the ‘
Interfaces’ screen, under the configuration menu for each sensor port
there is an On/Off toggle which can be set if Compatibility Mode is required for
that port.
6.13 Message 24 Content
The Unit Serial Number transmitted in AIS Message 24B, in response to a
Message 15 request, is encoded as follows (note that these characters repre-
sent individual bits in the data):
wwww wwyy yxxx xxxx xxxx
w = week (0 - 63)
y = years since 2014 (0 - 7)
x = incrementing number (0 - 2047)