Video Surveillance Glossary of Terms [I - J]

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• » IFrame [top]
  An IFrame is a complete image frame (known as an Intra Frame) in MPEG encoding that is coded without reference to other pictures.  Compression is achieved by reducing spatial redundancy in the image, but not temporal redundancy.
  
• » Image intensifier [top]
  This device is used to intensify low-level lighting conditions via light sensitive phosphor screens, and is specifically used to improve the performance of surveillance cameras in low light conditions.
  
• » Impedance [top]
  Measured in ohms, impedance describes the input and output characteristic of an electrical system.  For the best signal quality, both input and output impedances should be equal, with CCTV systems having 75-ohm impedance throughout.
  
• » Index of refraction [top]
  This ratio measures the angle of incidence to the angle of refraction of light, with a denser medium bending more light and having a higher index of refraction.
  
• » Infrared camera [top]
  These cameras are well suited for surveillance of low light areas or areas with no light at all.  Infrared LEDs surround the lens and shine infrared light, illuminating the scene.  They usually have a fixed focal length lens, and present b/w images during low light (though some offer color in the day and b/w at night). 
  
• » Infrared detector [top]
  This is an alarm that uses infrared light to detect nearby movement.
  
• » Infrared illuminator [top]
  A light source working in the infrared frequency range is called an infrared illuminator.
  
• » Infrared radiation [top]
  Invisible to the human eye, this electromagnetic radiation has a wavelength of greater than 750 manometers.
  
• » Injection molded plastic [top]
  Smoked or tinted plastic (but still translucent) is melted into a liquid from pellets and injected into a “dome-shaped” mold to construct security camera dome housings.
  
• » Insertion loss [top]
  If the inclusion of an electronic device into a line diminishes the signal’s strength, it’s called insertion loss.
  
• » Interlaced [top]
  This refers to a type of display where the electron beams alternate between scanning the even numbered lines and then the odd numbered lines, resulting in the two vertical scans on the screen, with the field (each set of lines) being updates 60 times a second, and with the frame (both fields) updated 30 times a second.
  
• » Interleaving [top]
  Some alarms and security systems use the process of interleaving to add extra frames from alarmed cameras to a time multiplexed sequence while the alarm is activated.  This prioritizes the view from alarmed cameras in the sequence of camera views.
  
• » IP (Internet Protocol) [top]
  This is the protocol used to route a packet of data from source to destination over the Internet.  Every computer on the Internet has a different IP address that identifies it from other computers.
  
• » IP address [top]
  This is a numeric address that is then translated into a domain name by the DNS (domain name server).  When we type in a website’s name, the computer translates this into its IP address, which is a unique 32-bit number.  The TCP/IP protocol then uses it for routing the data packets to their destinations.  Each host has a unique IP address.
  
• » IP Camera (or Network Camera) [top]
  This signal from an IP camera is delivered over an IP network.  The camera digitizes the images, compresses them, and then sends them over the network (if this sounds similar to a webcam, that’s because there is digital webcam technology contained within a network camera).  But a typical IP network camera is much more advanced as compared to a consumer web camera which needs to be attached to a computer to operate.  IP enabled security cameras usually offer a browser interface so that the user can operate and view the video remotely over the Internet.  A DVR system is often comprised of an IP camera and a NVR.
  
• » Iris [top]
  The section of the lens adjusted to control how much light passes through it and onto the CCD chip is called an iris. 
  
• » ISDN (Integrated Services Digital Network) [top]
  ISDNs are digital telecommunications lines that transmit voice and digital network services.  Many telephone companies provide them, due to their superior reliability and speed (up to 128K) over analog modems.  The ISDN standard improves compatibility for the integrated digital transmission of voice, video, and data over normal copper telephone wires, which allows for better quality and speeds.  There are two primary types of ISDN: BRI (Basic Rate Interface) and PRI (Primary Rate Interface).  PRI is faster, with speeds on par with T-1 circuits.
  
• » ITU (International Telecommunications Union) [top]
  Currently, 113 countries participate in the ITU, which is an agency of the United Nations.  Existent since 1865, the ITU is responsible for developing international telecommunications for networked telecommunications.  The ITU-R is a subchapter, and is responsible for managing radio frequency spectrum (including television and video) standards.
  
• » Joystick [top]
  PTZ controllers utilize this stick as a control device for pan and tilt movement of a PTZ security camera’s pan and tilt head.
  
• » JPEG (Joint Photographic Experts Group) [top]
  This is one of the most common file formats for compressed photo images. A small amount of data, though not noticeable enough to be significant, is lost in the compression process, making JPEGs a lossy compression algorithm.

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