Differential GPS (DGPS):A system of land-
based sites that broadcasts correction signals
for improved GPS position accuracy.
Electromagnetic compatibility (EMC):The
ability of electronic equipment to operate in
proximity with other electrical and electronic
equipment without suffering from, or causing,
impaired performance.
Electromagnetic interference (EMI):Elec-
tromagnetic or electrical disturbances that
result in undesirable responses, or impede the
performance of other electrical or electronic
equipment. For example, EMI is a common
cause of deviation in compasses and electronic
compass sensors.
Ethernet:Originally developed by Xerox in
1976, it now describes a diverse family of
frame-based computer networking technolo-
gies for local area networks (LANs). It is the
basis for IEEE standard 802.3.
False ground:For the purposes of this book, a
ground connection to neutral at a location
other than the source of power. In other words,
a point where an AC neutral conductor is
“falsely” connected to the AC grounding (earth)
conductor.
Galvanic isolator:A device installed in series
with a boat’s earth-ground conductor that
blocks low-level DC current (galvanic current)
but allows passage of AC fault current.
Ground fault circuit interrupter (GFCI):A
device intended to protect people by inter-
rupting an AC circuit whenever its current
limit is exceeded.
Ground fault protection (GFP) device:A
device intended to protect equipment by
interrupting the electric current to the load
when a fault current to ground exceeds a pre-
determined value. Also known as an RCD
(residual current device) or an EPD (equip-
ment protecting device).
Harmonic distortion:A load where the wave
shape of the steady-state current does not followthe wave shape of the applied voltage. The
presence of harmonics that change the AC
voltage waveform from a simple sinusoidal
waveform to a complex waveform. Harmonic
distortion can be generated by a load and fed
back into the AC mains, causing power prob-
lems to other equipment on the circuit.
Impedance:The opposition to the flow of
alternating current in a circuit. It’s the high-
frequency equivalent of resistance.
Inductance:A property of a conductor or coil
that determines how much voltage will be
induced in it by a change in current.
Ingress protection (IP):An internationally
recognized standard that addresses both water
ingress and dust ingress into equipment. The
higher the IP number assigned to a given piece
of equipment, the more waterproof and dust-
proof it is.
Inmarsat:A satellite communications com-
pany that provides voice and data services to
the maritime, transportation, and aeronautics
markets as well as providing general Internet
access from any location on the globe. It was
founded in 1979 as a British intergovernmen-
tal organization (IGO) to serve the maritime
industry. It became a private company in 1999
and a public company in 2005.
Institute of Electrical and Electronics Engi-
neers (IEEE):A nonprofit organization that cre-
ates internationally recognized standards applica-
ble to electrical and electronic equipment.
International Maritime Organization
(IMO):A specialized agency of the United
Nations that develops standards for safety at
sea, shipping security, and prevention of water
pollution as related to ships.
Japanese Industrial Standard (JIS):Specifies
the standards used for industrial activities in
Japan.
Linear load:In this context, a simple resistive
load that draws current in proportion to the
voltage delivered. For example, a simple206 glossary