DOSDisk Operating System.HOMING SWITCHERTerm used to describe a sequential switcher with only one output.LIGHT SENSORA device that is activated when a preset amount of light is present on the sensor. This can result in picture smearing, which is a major shortcoming of this device. Normally has a focusing control and a choice of iris functions.ERGONOMICSThe study of man, machine and the working environment to achieve maximum efficiency. 1 Hertz = 1 cycle per second. Only used where the distance between controller and controlled device is short. An electronic chip used in many different security products, which stores software instructions for performing various operations. This is used to prevent picture "bounce" when switching between cameras and can improve the overall quality and update time of recordings when using switchers or multiplexers. This type of chip overcomes many of the shortcomings of the existing CCD chips used in CCTV cameras. Signals can be degraded over long distances or in adverse weather conditions. Depth of field increases when the f-stop is greater, the focal length shorter or the distance to the object is increased.ENG CAMERAElectronic News Gathering camera usually refers to CCD cameras in the broadcast industry.DSPDigital Signal Processing. Usually refers to power, but can also be used for voltage and current. Depth of field varies depending on the f-stop and focal length of a lens. The result of this is noise (interference) introduced in the signal.EASElectronic Article Surveillance.LINEThe basic unit of a frame or field containing the charge, which is proportional to the light falling at various points on the scanning line.FRAME INTERLINE CHIPA type of CCD imaging device, which is expensive to manufacture and is currently used in broadcast quality cameras.IP RATINGIndex of protection that refers to the level of protection provided by equipment housings, against the ingress of dust or moisture.DCDirect Current.INDEX OF REFRACTIONThe ratio between the angle of incidence to the angle of refraction of light.

LENS WHEELSee Lens calculator. electrical circuit.ISDN(Integrated Services Digital Network).INFRARED TRANSMISSIONMethod of transmitting signals using an infrared beam.INFRARED LIGHTLight produced at the red end of the spectrum.LUXUnit of illumination. In CCTV refers to the part of the video signal that contains information about the scene brightness.LAN(Local Area Network).HERTZThe unit of measurement for frequency in a signal.LOOPING SWITCHERRefers to a type of switcher where signals are looped through the switcher without being affected by the operation of the switcher itself. American Association that sets the standard for video broadcast in the USA and Canada (525 lines, 30 frames per second).INTERLINE TRANSFERA type of CCD imaging device in which the charge is processed according to the amount of light falling on the sensors and then transferred immediately. This charge is then converted into an analogue video signal. Measured in Ohms.INTERFERENCEEffect caused by the introduction of unwanted electrical signals into an electrical circuit.GAMMA CORRECTIONA method of correction used in cameras to balance the brightness seen by a camera to that of the monitor. In CCTV this source of exceptionally pure light can be used to transmit signals along fibre optic cables, providing very high quality signal and data transmission.EPROMErasable and Programmable Read Only Memory.DARK NOISENoise caused by the random (quantum) nature of the dark current. Refers to an electronic circuit capable of processing digital signals.DUPLEXA system that is capable of handling two channels of information simultaneously.FLY BACK PERIODThe time taken for a signal to move from the end of a field, frame or line to the start of the next field frame or line.FOCUSING RINGRing on the outside of a lens to allow adjustment to obtain correct focus.DOMETerm used to describe a type of camera housing made of smoked glass or plastic usually containing a pan and tilt head and used for discreet surveillance. A semiconductor that produces light when stimulated by an electric current. 1 Lumen = amount of light emitted by a light source of 1 Candela.DE-MULTIPLEXINGThe process of separating different video, audio, or data signals, which were multiplexed at source.FIELDHalf of a single frame, consisting of either the odd or even lines. In CCTV, duplex is used to describe a multiplexer that can record in multiplex mode whilst simultaneously displaying multi-screen pictures.ELECTRON BEAMA concentrated flow of electrons in a nominated direction.IMAGE INTENSIFIERA devise used to intensify light through the use of light sensitive phosphor screens. Telecommunications network that is capable of transmitting digital signals at speeds of up to 128kb/sec.GUI(Graphical User Interface).

LENSAn optical device for focusing light onto the imaging device in a camera.IRISThe part of a lens that is used to control the amount of light that passes through the lens and onto the imaging device.LENS CALCULATORA calculator used to calculate the most suitable lens to provide an image of a given scene when used with a specific camera.FOCAL LENGTHThe distance between the optical centre of a lens and the focal point.HORIZONTAL RESOLUTIONThe number of vertical lines that can be resolved in a picture. Interference caused by an item of electrical equipment radiating electro magnetic frequencies.LUMINOUS FLUXThe rate of flow of light.DARK CURRENTLeakage signal from a CCD sensor in the absence of incident light.DWELL TIMEWhen relating to video switchers this is the time that a picture remains on a monitor before being replaced by the next picture..FRAME SWITCHERA basic form of multiplexer, which can be used to record multiple cameras on a single VCR.LENS HUNTINGA problem encountered when an auto iris lens opens and closes alternatively because it is unable to find the correct level. Index varies depending on the density of the medium.GALVANOMETERIn CCTV this term refers to a method of operating an auto iris lens.GROUND LOOP CURRENTIn CCTV this term refers to a current that is produced in a cable as a result of a difference in earth potential existing at each end of the cable. Found between the inner core and outer shield of a co-axial cable.ILLUMINANCEThe amount of light, which falls onto a given surface area. Measured in lux.DIGITAL SIGNALAn electronic signal, which is represented by binary numbers, and that, can be processed by a microprocessor, or stored in an electronic memory.INTERLACINGThe process of combining odd and even fields to form a frame. 1 Foot-candela =1 Lumen of light incident on 1sq ft of surface area. In a PAL system this is 312. Not visible to the naked human eye.INFRARED ILLUMINATORLight source, which emits light in the infrared part of the spectrum. System used in retail stores to prevent shoplifting by attaching tags to the merchandise, which activate an alarm when passed through detectors. Measured in Lumens per square metre.FIBRE OPTICA very efficient method of transmitting video and telemetry signals over long distances using a light beam transmitted along a fibre optic cable constructed from high density Silica Glass. A term used to describe the interface between a computer screen and the user.DECIBEL (DB)A logarithmic ratio between two electrical signals or values. Means of connecting a number of computers to enable communication between each device connected to the network.c. In CCTV these are used as the light source in some fibre optic transmission systems, and as light the light source for illuminating scenes for use with Monochrome cameras. 1 Lux = the amount of uniform light falling onto a surface of 1sq metre.FIXED LENSA lens with a pre-determined fixed focal length.

The denser the medium, the higher the index. Can be a stand-alone unit or incorporated in other equipment such as fast scan transmitters or video motion transmitters. Used to intensify camera performance under low light conditions. Now used in CCTV Systems to describe features such as touch screen control of systems and equipment.FIELD OF VIEWThe height and width of view that can be seen through a lens. In CCTV this results in "noise" in the signal or picture, which disrupts the picture.HORIZONTAL SHIFT REGISTERPart of the CCD image device to which the charge from the pixels is transferred line by line. The changing light level causes a change in the current induced into a minute coil, which in turn causes movement in the Iris diaphragm.IMPEDANCEThe total opposition to current flow in Single-Phase Relays Suppliers an a.LUMENUnit of light measurement of light radiation.EIAElectronics Industry Association.EMIElectro Magnetic Interference. Allows CCTV signals to be transmitted where cables cannot be run. Available in a range of sizes to suit different applications.DIELECTRICAn insulating (non-conductive) material. These systems are often interfaced with CCTV systems.GROUND LOOP INSULATORA transformer with no direct connection between the inputs and outputs, used to eliminate Ground Loop Currents.LENS MOUNTSee C-mount or CS-mount.FRAME TRANSFERA type of CCD Imaging device in which the pixels have a dual role of sensing the light and transferring the charge.FRAME STOREAn electronic device used to capture and digitally store a video image.IMAGING DEVICEA 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.5 lines.EBUEuropean Broadcasting Union. A software package that makes a computer work with its hardware devices such as hard drive, floppy drive, screen, keyboard, etc.LINE-LOCKEDRefers to a method of synchronising cameras to a common AC frequency.DEPTH OF FIELDThe distance between the nearest and furthermost object in a scene which appear in sharp focus.HARDWIREDRefers to a method of controlling CCTV equipment by using multi-cored cable run between the controller and device to be controlled.LED(Light Emitting Diode).

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