B&G NSPL-400 - Manual (Page 7)

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About your AIS/VHF antenna splitter | NSPL-400 User Manual
About your AIS/VHF antenna splitter
About AIS
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 vessels. Position is derived from the
Global Positioning System (GPS) and communication between ves-
sels is by Very High Frequency (VHF) digital transmissions.
There are a number of types of AIS device as follows:
• Class A transceivers. These are similar to class B transceivers but
are designed to be fitted to large vessels such as cargo ships and
large passenger vessels. Class A transceivers transmit at a higher VHF
signal power than class B transceivers and therefore can be received
by more distant vessels, and also transmit more frequently. Class A
transceivers are mandatory on all vessels over 300 gross tonnes on
international voyages and certain types of passenger vessels under
the SOLAS mandate.
• Class B transceivers. Similar to class A transceivers in many ways,
but are normally lower cost due to the less stringent performance
requirements. Class B transceivers transmit at a lower power and at a
lower reporting rate than class A transceivers.
• AIS base stations. AIS base stations are used by Vessel Traffic Sys-
tems to monitor and control the transmissions of AIS transceivers.
• Aids to Navigation (AtoN) transceivers. AtoNs are transceivers
mounted on buoys or other hazards to shipping which transmit
details of their location to the surrounding vessels.
• AIS receivers. AIS receivers will generally receive transmissions
from class A transceivers, class B transceivers, AtoNs and AIS base sta-
tions but do not transmit any information about the vessel on which
they are installed.
Because VHF radios and AIS devices operate within the same fre-
quency range and therefore require the same type of VHF antenna it
is possible to utilise a single VHF antenna for both devices by using
an AIS/VHF antenna splitter.
The NSPL-400 is designed to work primarily with AIS class B trans-
ceivers, although it will operate equally well with AIS receivers.
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