Comar Systems CSB200 Installation And Instruction Manual page 5

CSB200 Class B AIS
INTRODUCTION
Automatic Identification Systems (AIS)
How AIS Works
The marine Automatic Identification System (AIS) is a location and vessel
information reporting system. It allows vessels equipped with AIS to
automatically and dynamically share and regularly update their position,
speed, course and other information such as vessel identity with similarly
equipped craft. Position is derived from a Global Navigation Satellite
System (GNSS) network and communication between vessels is by Very
High Frequency (VHF) digital transmissions. A sophisticated and
automatic method of time sharing the radio channel is used to ensure that
even where a large number of vessels are in one location blocking of
individual transmissions is minimised, any degradation of the expected
position reporting interval is indicated to the user and even if the unit
suffers extreme channel overload conditions it will always recover to
normal operation.
AIS Classes
There are two classes of AIS unit fitted to vessels, Class A and Class B.
In addition AIS base stations may be employed by the Coastguard, port
authorities and other authorised bodies. AIS units acting as aids to
navigation (A to Ns) can also be fitted to fixed and floating navigation
markers such as channel markers and buoys.
Class A units are a mandatory fit under the safety of life at sea (SOLAS)
convention to vessels above 300 gross tons or which carry more than 11
passengers in International waters. Many other commercial vessels and
some leisure craft also fit Class A units.
Class B units are currently not a mandatory fit but authorities in several
parts of the world are considering this. Class B units are designed for
fitting in vessels which do not fall into the mandatory Class A fit category.
The CSB200 is a Class B unit
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