IDE. Interface device electronics. Software and hardware communication standard for interconnecting peripheral devices to a computer. I/O. Input/Output. I/P. Input. A signal applied to a piece of electric apparatus or the terminals on the apparatus to which a signal or power is applied. I2R. Formula for power in watts (W), where I is current in amperes (A), R is resistance in ohms (W). IEC. International Electrotechnical Commission (also CEI). Imaging device. A vacuum tube or solid state-device in which the vacuum tube light-sensitive face plate or solid-state light-sensitive array provides an electronic signal from which an image can be created. Impedance. A property of all metallic and electrical conductors that describes the total opposition to current flow in an electrical circuit. Resistance, inductance, capacitance and conductance have various influences on the impedance, depending on frequency, dielectric material around conductors, physical relationship between conductors and external factors. Impedance is often referred to with the letter Z. It is measured in ohms, whose symbol is the Greek letter omega - W. Input. Same as I/P. Inserter (also alphanumeric video generator). A device for providing additional information, normally superimposed on the picture being displayed; this can range from one or two characters to full-screen alphanumeric text. Usually, such generators use the incoming video signal sync pulses as a reference point for the text insertion position, which means if the video signal is of poor quality, the text stability will also be of poor quality. Interference. Disturbances of an electrical or electromagnetic nature that introduce undesirable responses in other electronic equipment. Interlaced scanning. A technique of combining two television fields in order to produce a full frame. The two fields are composed of only odd and only even lines, which are displayed one after the other but with the physical position of all the lines interleaving each other, hence interlace. This type of television picture creation was proposed in the early days of television to have a minimum amount of information yet achieve flickerless motion. Interline transfer. This refers to one of the three principles of charge transferring in CCD chips. The other two are frame transfer and frame-interline transfer. IP. Index of protection. A numbering system that describes the quality of protection of an enclosure from outside influences, such as moisture, dust and impact. IRE. Institute of Radio Engineers. Units of measurement dividing the area from the bottom of sync to peak white level into 140 equal units. 140 IRE equals 1Vpp. The range of active video is 100 IRE. IR light. Infrared light, invisible to the human eye. It usually refers to wavelengths longer than 700 nm. Monochrome (B/W) cameras have extremely high sensitivity in the infrared region of the light spectrum. Iris. A means of controlling the size of a lens aperture and therefore the amount of light passing through the lens. ISDN. Integrated Services Digital Network. The newer generation telephone network, which uses 64 kb/s speed of transmission (being a digital network, the signal bandwidth is not expressed in kHz, but rather with a transmission speed). This is much faster than a normal PSTN telephone line. To use the ISDN network you have to talk to your communications provider, but in general a special set of interface units (like modems) are required. ISO. International Standardization Organization. ITU. International Telecommunications Union (also UIT). JPEG. Joint Photographic Experts Group. A group that has recommended a compression algorithm for still digital images that can compress with ratios of over 10:1. Also the name of the format itself. kb/s. Kilobits per second. Thousand bits per second. Also written as kbps. Kelvin. One of the basic physical units of measurement for temperature. The scale is the same as the Celcius, but the 0ºK starts from -273ºC. Also the unit of measurement of the temperature of light is expressed in Kelvins or K. In color recording, light temperature affects the color values of the lights and the scene that they illuminate. K factor. A specification rating method that gives a higher factor to video disturbances that cause the most observable picture degradation. kHz. Kilohertz. Thousand Hertz. Kilobaud. A unit of measurement of data transmission speed equalling 1000 baud. Kilobyte. 1024 bytes. Lambertian source or surface. A surface is called a Lambert radiator or reflector (depending whether the surface is a primary or a secondary source of light) if it is a perfectly diffusing surface. LAN. Local Area Network. A short distance data communications network (typically within a building or campus) used to link together computers and peripheral devices (such as printers, CD ROMs and modems) under some form of standard control. Laser. Light amplification by stimulated emission of radiation. A laser produces a very strong and coherent light of a single frequency. LED. Light Emitting Diode. A semiconductor that produces light when a certain low voltage is applied to it in one direction. Lens. An optical device for focusing a desired scene onto the imaging device in a CCTV camera. Level. When relating to a video signal it refers to the video level in volts. In CCTV optics, it refers to the auto iris level setting of the electronics that processes the video signal in order to open or close the iris. Line-locked. In CCTV, this usually refers to multiple cameras being powered by a common alternative current (AC) source (either 24 V AC, 110 V AC or 240 VAC) and consequently have field frequencies locked to the same AC source frequency (50 Hz in CCIR systems and 60 Hz in EIA systems). Liquid crystal display (LCD). A screen for displaying text/graphics based on a technology called liquid crystal, where minute currents change the reflectiveness or transparency of the screen. The advantages of LCD screens are very small power consumption (can be easily battery driven) and low price of mass-produced units. The disadvantages are narrow viewing angle, slow response (a bit too slow to be used for video), invisibility in the dark unless the display is back lighted, and difficulties displaying true colors with color LCD displays. Lumen [lm]. A light intensity produced by the luminosity of 1 candela in one radian of a solid angle. Luminance. Refers to the video signal information about the scene brightness. The measurable, luminous intensity of a video signal. Differentiated from brightness in that the latter is nonmeasurable and sensory. The color video picture information contains two components, luminance (brightness and contrast) and chrominance (hue and saturation). The photometric quantity of light radiation. LUT. Look-up table. A cross-reference table in the computer memory that transforms raw information from the scanner or computer and corrects values to compensate for weakness in equipment or for differences in emulsion types. Lux [lx]. Light unit for measuring illumination. It is defined as the illumination of a surface when luminous flux of 1 lumen falls on an area of 1 m2. It is also known as lumen per square meter, or meter-candelas.