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H
 HAD.  Hole Accumulated Diode.  A type of CCD sensor with a layer designed to accumulate
holes (in the electronic sense), thus reducing noise level.
HDD.  Hard Disk Drive.  A magnetic medium for storing digital information on most computers
and electronic equipment that process digital data.
HDDTV.  High Definition Digital TeleVision.  The upcoming standard of broadcast television
with extremely high resolution and aspect ratio of 16:9.  It is an advancement from the analogue
high definition, already used experimentally in Japan and Europe.  The picture resolution is nearly
2000×1000 pixels, and uses the MPEG-2 standard.
HDSL.  High-bit-rate Digital Subscriber Line.  A digital transmission path that can be used for the
transmission of  CCTV pictures (1 camera) at up to 2Mbps.  Up to 5 cameras can be transmitted
but the data rate is shared (i.e. 384kbps for each camera).
HDTV.  High Definition TeleVision.  It usually refers to the analogue version of the HDDTV.
Headend.  The electronic equipment located at the start of a cable television system, usually
including antennas, earth stations, preamplifiers, frequency converters, demodulators, modulators
and related cable transmission equipment.
Helical scan.  A method of recording video information on a tape that increases the "density"
of recorded information on tape, when compared with linear recording.  It is used commonly in
both home and professional VCRs.
Horizontal Drive (also Horizontal sync).  This signal is derived by dividing sub-carrier by
227.5 and then doing some pulse shaping.  The signal is used by monitors and cameras to
determine the start of each horizontal line.
Horizontal resolution.  Chrominance and luminance resolution (detail) expressed horizontally
across a picture tube, it is often given as TeleVision Lines (TVL).  This is usually expressed as
a number of black to white transitions or lines that can be differentiated.  Limited by the
bandwidth of the video signal or equipment.
Herringbone.  Patterning caused by driving a colour-modulated composite video signal (PAL
or NTSC) into a monochrome monitor.  It is also often a characteristic of Radio Frequency
Interference (RFI) picked up along a coaxial cable length.
Horizontal retrace.  At the end of each horizontal line of video, a brief period when the
scanning beam returns to the other side of the screen to start a new line, sometimes called
flyback.
Horizontal sync pulse.  The synchronizing pulse at the end of each video line that determines
the start of horizontal retrace.
Hertz.  The unit that measures the number of cycles per second.  Named after Heinrich
Rudolph Hertz, a physicist.
Housings, environmental.  Usually refers to the containment of the camera and lenses and
associated accessories, such as heaters, washers and wipers, to meet specific environmental conditions.
HS.  Horizontal synchronization.
Hue (tint, phase, chroma phase).  One of the characteristics that distinguishes one colour from
another.  Hue defines colour on the basis of its position in the spectrum, i.e., whether red, blue,
green or yellow, etc.  Hue is one of the three characteristics of television colour: see also Saturation
and Luminance.  In PAL and NTSC video signals, the hue information at any particular point in the
picture is conveyed by the corresponding instantaneous phase of the active video subcarrier.
Hum.  A term used to describe an unwanted induction of mains frequency.
Humbug.  A trade name for an isolation transformer (to remove earth or ground loops).
Hyper-HAD.  An improved version of the CCD HAD technology, utilizing on-chip micro-lens
technology to provide increased sensitivity without increasing  the pixel size.
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