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The RC10 can determine potential odds of collision.
Our device is composed of
- a highly sensitive specific receiver adapted for simultaneous performance on
both A.I.S. frequencies: F1=161.975 MHz and F2=162.025 MHz.;
- an alarm calculator which will work out the CPA ( Closest Point of Approach
) as well as the TCPA ( Time to CPA ), in order to activate an alarm according to a
predetermined alarm level option graded from one to four.
Thus, the RC10 is primarily meant to keep a thoroughly independent watch
function. However, if needed, it transforms AIS indications received into ‘normalized’
NMEA/AIS messages transferred onto a PC.
To make sure the RC 10 works properly, it is advisable to select alarm level 1
in the sort of environment most adapted for reception of an I.A.S. message ( ship on sight,
harbour, etc ).
The alarm / Basic principles
An alarm is activated as soon as the criteria defined by the selected level of
alarm have reached the corresponding calculations obtained for CPA and TCPA. For
example:
In case we chose level 3 ( CPA < 4 miles and TCPA < 20 minutes ), there will
be an alarm if and only if the CPA obtained is inferior to 4 miles and TCPA inferior to 20
minutes.
Which means that a slow-moving vessel, located 3 miles away, whose CPA is
of 2 miles—but won’t reach that distance before 20 minutes have elapsed—will not activate
any alarm, whereas a fast-moving ship located 8 miles away, but whose CPA is of 3 miles,
with a 15- minute TCPA, will.
In a similar way, any vessel located only 3 miles away, but undergoing a
process of increasing distance, will not activate an alarm. However, for safety reasons, any
ship located within a mile will provoke an alarm, whatever her route may be.
Thus, it is now easy to understand that the alarm criteria do not depend from the
ship’s position ( except when it is inferior to 1mile ), but are calculated to prevent any risk of
the ship getting nearer ( distance / speed ).
On the other hand, localization of the ship by means of the LEDS ( positioning /
distance ) does correspond to her real-time whereabouts.
In the particular case of an alarm being activated for a ship located within one
mile, the alarm signals are provided by the red LEDS ( positioning ), the green LED light
being kept on permanently ( instead of indicating distance in miles ). The rest of the time, the
number of green LED light ‘flashes’ clearly indicates that distance from the ‘hazardous’ ship
on a very simple mode ( 1 flash = 1 mile / thus, anything from “1 , 0 “ to “ 1 , 9 “ –-number
of flashes being limited to ten ).
And as for the sound alarm, it has been indexed in function of the risk.
Thus, for example, far-distant ships on level 1 will only provoke a short buzz,
whereas a closer CPA and a shorter TCPA will entail a longer activation of the
buzzer.
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