Video Surveillance Glossary of Terms [G - H]

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• » Gamma correction [top]
  This refers to an automated correction installed into surveillance cameras that adjusts for the brightness characteristic of the monitor, with the range being from .6 to 1.
  
• » Gen-lock [top]
  The use of composite video, composite sync, or vertical or horizontal sync to synchronize one or more cameras is known as Gen-lock.
  
• » Ghost [top]
  Also known as ghosting, this is when an image moved across a computer screen leaves a brief lingering shadow of itself where it had just been, creating a kind of smear or blur.  Lower quality computer screens often leave ghosts.  Technically, the secondary visual signal has been created and received either earlier or later than the primary signal itself.
  
• » Ground Loop [top]
  This type of picture interference is caused when the ends of a video cable have differing ground potential, causing an AC current.  This is either a black shadow bar onscreen or a tearing in the top corner of the picture results. The use of ground loop insulators prevents this problem.
  
• » GUI (Graphical User Interface) [top]
  Pronounced ‘gooey’, this is the interface between the computer and the matrix switcher.  Active areas of the computer screen are programmable, feature menus, icons, are clickable, and able to activate devices such as VCRs and matrix switchers.  Essentially, the GUI makes the CCTV system easier to use.
  
• » Hertz [top]
  A Hertz (Hz) is the unit used to measure frequency, with 1 Hz equal to 1 cycle per second.
  
• » Horizontal hum bars [top]
  Sometimes called Venetian blinds because they are horizontal bars (either black or white) that extend across an entire picture.  They’re either moving or stationary, and are the result of roughly a 60 Hz interfering frequency (usually from a 60 Hz AC power source). 
  
• » Horizontal resolution [top]
  This measures the maximum amount of individual picture elements recognizable in a single scanning line.
  
• » HTML (HyperText Markup Language) [top]
  HTML is the language used in the creation of WWW pages, with use of hyperlinks and markup for text formatting. 
  
• » HTTP (HyperText Transfer Protocol) [top]
  This is the protocol utilized to transmit and request information from WWW servers to browsers, either online or over networks.
  
• » Hub [top]
  Networks rely on devices called hubs to connect multiple computers together into a LAN.  Standard hubs share the bandwidth across all ports (so an eight port 100 Mps hub allocates this 100 Mps among the eight ports), while switching hubs are able to give each individual port a dedicated bandwidth amount (so these same eight ports could conceivably each receive a full 100 Mps of bandwidth on a switching hub).

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