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Glossary of Terms

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Automatic Gain Control. An electronic circuit that tries to keep the video signal at a constant level (1volt peak-peak). Useful on cameras working at low light levels.


Auto Iris. An electronic circuit that acts as an iris on CCD camera's by electronically shuttering the CCD sensor.


As Low As Reasonably Achievable. Making every reasonable effort to maintain exposures to radia tion as far below the dose limits as is practical and consistent with the purpose for which the licensed activity is undertaken.

Ambient Light Level

General level of light in a given area before specific lighting is added for CCTV cameras.

Analogue Video

A video signal conforming to CCIR or RS170 specification.

Angle of View

The angle from which a lens collects light, a description of the area that will be seen on a video picture using a particular lens.


A measure of a len's light gathering efficiency measured in f-numbers.

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The most commonly used video cable connector.

Back Focus (also known as RACKING)

As Macro focus, a method of moving the image sensor backward and forward with respect to the lens to obtain a close focus facility. Very important on Zoom lenses to ensure that the image stays in focus throughout the zoom range.

Balanced Signal

A method of transmitting video over a twisted pair cable that consists of two equal but opposite signals being sent down the two conductors.


A filter that divides an image into two separate paths. Typically made from metal-coated glass designed to be 45° incident to the incoming image.


Instrument that provides a temperature source for on-site or in laboratory calibration of radiation thermometers.

Boiling-Water Reactor

A reactor whose primary coolant is allowed to boil.

Breeder Reactor

A reactor which produces more fissile material than it consumes, i.e., has a conversion ratio greater than unity.

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Letter denoting the color portion of the video signal.


SI Unit of luminous intensity (a measurement of light output from a source).


Charged Coupled Device. A solid-state image sensor that transfers photo-generated charges via a 'bucket bridge' delay line.

CCD Iris

Automatic adjustment of a CCD device's 'exposure time' (particularly useful when using fixed aperture lenses).


Comite Consulatif International des Radiocommunications. The European TV standard - 625 lines 50 Hz.


Closed Circuit Television. Standard camera equipment using NTSC/PAL video timing. Can be viewed on standard composite monitor.


Camera Control Unit. Contains the power supplies and electronic circuits the drive a dual unit camera and obtain a standard video signal.


Committed Dose Equivalent, HT.50 (Internal). Dose equivalent to organs or tissues of reference (T) that will be received from an intake of radioactive material by an individual during the 50-year period following the intake.


Committed Effective Dose Equivalent. HE (Internal). Sum of the products of the weighting factors and committed dose equivalent to each of the body organs or tissues that are irradiated.


A type of sensor tube that has a target layer based on cadmium selenide (face plate material).


The color information contained in a composite video signal.

C Mount

A standard fitting for connecting lenses to cameras.

Coax Cable

Cable of 75ohm impedance used to carry video signals.

CS Mount

Another standard for fitting lenses to cameras, it has shorter penetration than C mount.


Composite Video Signal. The standard output from an analogue video camera, consisting of all the amalgamated parts of the video signal, such as Chrominance, Luminance and Synchronization pulses.

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D Mount

A smaller sized standard for fitting lenses to cameras, used on IST R93 and R980 series cameras.


Deep Dose Equivalent. Measurement in rem for dose equivalent at a tissue depth of 1 cm; applies to external whole body exposure.

Depth of Field

The area of acceptable focus in front of and behind a subject that is being viewed. The wider you set the aperture of a lens the lower the depth of field becomes.

Digital Video

The representation of a video signal by binary code.


The energy absorbed from the radiation in a gram of any material.

Dose Equivalent

The product of the absorbed dose in tissue, quality factor, and all other necessary modifying factors at the location of interest.

Dual Unit Camera

A camera head that must be connected to a CCU to obtain video signals.

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Emergency Preparedness Department.

Effective Dose Equivalent

Risk-weighted sum of products of dose equivalents to major body organs or tissues that are irradiated.

EIA (Electronic Industry Association)

U.S.A. TV standard - 525 lines 60Hz.

Endoscope Camera

The camera that has been designed jointly between IST and BNFL for through-wall and roof viewing applications in radiation environments.

External Dose

That portion of the dose equivalent received from radiation sources outside the body.


Hand, elbow, arm below the elbow, foot, knee, leg below the knee.

Ext. Sync. (External Synchronization)

Synchronization pulses derived from a source other than the camera itself that lock the timing of the video line or field signal from that camera to other devices. These devices may include other cameras, pulse generators, switching equipment, or text generation equipment.

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Faceplate Illumination

The amount of light (specified in Lux) required on the sensor faceplate to produce a specified video output level (typically 50%). Note that this method does not take into account the lens.

Faceplate Materials

Two types of faceplate materials are available for monochrome radiation tolerant cameras Chalnicon and Vidicon. Chalnicon tubes provide a greater sensitivity, better temperature stability and are less sensitive to image burn than Vidicon tubes. Vidicon tubes, however, can operate at higher dose rates than Chalnicon tube, 1M rad/hour as opposed to 100Krads/hour, and should only be in environments where the dose rate is greater than 100krads/hour. Color radiation tolerant cameras are also available based on a Saticon faceplate material.

Field of View

The overall view achieved by a lens.

Focal Length

The distance between a lens' secondary principal point and its focal point. The higher the number the greater the magnification and the less the field of view.

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Gen. Lock

To synchronize one piece of video equipment to the sync. pulses of another.


(Gy) SI unit of absorbed radiation (equal to 1 joule per Kilogram).

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Health Physics

The science concerned with the recognition, evaluation and control of health hazards from ionizing radiation.

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The amount of light (specified in Lux) entering a lens, at a specified aperture (f-number), that is required to produced a specified video output level (typically 50%).

Image Sensor

Format The size of a camera's image sensor (CCD or Tube). Important to note when selecting an appropriate lens.

Internal Sync.

A piece of video equipment that generates its own synchronization pulses. Normally using a crystal controlled oscillator.

Ionizing Radiation

Alpha particles, beta particles, gamma rays, x-rays, and other particles capable of producing ions.


Part of a lens that is adjusted to restrict or increase the amount of light passing through the lens to the sensor.


Integrated Services Digital Network. Digital telephone lines that allow the transmission of data and digitized video signals.

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LDE: Eye Dose Equivalent.

Measurement in rem for dose equivalent at a tissue depth of 0.3 cm; applies to the external exposure of the lens of the eye.

Leak Test

Testing for alpha, beta, or gamma emitting radiation sources.


Individual dose limits which includes planned special exposures and overexposures. Annual 5 rem TEDE, 15 Rem LDE and 50 Rem SDE-WB and SDE-ME.

Line / Launch Amplifier

A device that boosts analogue video signals in order to transmit them over long cable lengths.


Lighting Power Supply Unit.

LSF Cable

Low Smoke and Fume. A cable that's outer sheathing is manufactured from material that will not burn easily and does not emit large amounts of smoke and fumes. LSF sheathed cables are not waterproof, although will withstand some water spray. (R000CAB035 is an LSF version of TV 36)

Lumin (lm)

The SI unit of luminous flux.


The brightness (or black and white) information contained in a video signal.

Lux (lx)

The SI unit of light illuminance (equal to 1 lm per square meter).

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Macro Focus

A method of moving the image sensor backward and forward to obtain a close focus facility.

Matrix Switcher

A piece of equipment, which is employed in larger systems to route a number of camera outputs to a selection of video monitors.

Mechanical Focus

As MACRO Or BACK FOCUS, except that the sensor is moved backwards and forwards by making a mechanical adjustment to the camera. Usually a screw adjustment on a CCD camera. This term can also be used to describe the mechanical adjustment on a lens.

Mini Cable

A narrow diameter radiation tolerant underwater CCTV cable specifically designed by IST for situations where flexibility is necessary. Can be coiled for use on mobiles.

Mini-Kevlar Cable

A radiation tolerant underwater cable specifically designed by IST, containing 24 cores of various types specifically for CCTV applications. Includes a Kevlar strength member.


A unit used to measure the effect of radiation on the human body.


A device for splitting a number of signals into elements and combining them to permit transmission down a single cable. Video signals are usually divided into lines or fields. The signals are reconstituted into their original form after transmission.

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Neutral Density. A filter used on lenses that attenuates light uniformly over the whole visible spectrum (as in N.D. spot). Used to change or increase the lighting intensity range (dynamic range) of a camera.


National Television Standards Committee. Color TV system used in the U.S.A., Canada, Mexico, Japan and many other countries. - see EIA.

Nuclear Reactor

An apparatus in which nuclear fission may be sustained in a self-supporting chain reaction. A reactor includes fissionable material (fuel) such as uranium or plutonium, and moderating material (except fast reactors), and usually includes a reflector to conserve escaping neutrons, provision for heat removal, and measuring and control elements. The terms "pile" and "reactor" have been used interchangeably, with reactor now becoming more common. These terms usually are applied only to systems in which the reaction proceeds at a controlled rate, but they have also been applied to bombs.

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Occupational Dose

Dose received by an individual in a restricted area or in the course of employment in which the individual's assigned duties involve exposure to radiation and/or to radioactive material from licensed and unlicensed sources of radiation, whether in the possession of the licensee or other person. Occupational dose does not include dose received from background radiation, as a patient from medical practices, from voluntary participation in medical research programs, or as a member of the general public.

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Phase Alternate Line. Color TV system used by many Asian and European countries, including the UK. - see CCIR

Passive Dosimeters

A device used to measure the dose of ionizing radiation received by an individual. There are many types of dosimeters with varying characteristics and capabilities appropriate for different applications. They differ in sensitivity, energy range, and species of radiation to which they respond. Some can be read out directly by the wearer, while others must be sent to a specially equipped facility to determine the dose.


An operation programmed into a control system. This allows the operation to be replicated automatically, i.e. a camera outstation can be programmed (preset) to drive the pan & tilt unit and the lens functions to view a particular target at a specific command or alarm signal.

Pressurized-Water Reactor

A reactor whose primary coolant, water, is maintained under such a pressure that bulk boiling does not occur.


Planned Special Exposures (Reg Guide 8.35). Restricted to special circumstances where the dose to the individual cannot otherwise be avoided, and, which causes the annual limit for that individual to be exceeded. The PSE provides for an additional dose, equal to the annual limit, to be used by the individual, after a thorough evaluation is conducted which justifies the additional dose is absolutely necessary to complete the job requirements, and, where no other individual is available.


Power Supply Unit.


Non-contact measurement of temperature based on emitted radiation, and the emissivity of a material.

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An industry standard size for electronic enclosures - can be 19 inch or 24 inch. IST standardize on 19 inch. (The width of the enclosures is 19" and height is measured in 'U' size. 1U = 1.75").


Unit of absorbed radiation (100 rad is equal to 1Gy).

Radiological Health

The art and science of protecting human beings from injury by radiation, and promoting better health through beneficial application of radiation.

Real Time Dosimeters

Devices for measuring radiation that offer real time dose and dose rate measurements.


Roentgen Equivalent Man. The product of the absorbed dose in tissue, quality factor, and all other necessary modifying factors at the location of interest. "Unit of dose equivalent" (1 rem=0.01 sievert)


Red Green Blue. A common video format consisting of three primary color signals used in the color transmission standards of NTSC, PAL and SECAM. Most have the sync pulse on the Green input, however some may require an external sync.


Recommended Standard 232. A recommended industry standard method for transmitting data. RS232 allows Full Duplex transmission, which means there are separate transmit and receive signal lines enabling data flow in both directions simultaneously. RS232 uses an unbalanced signal mode, meaning a voltage down a single wire is used to transmit/receive binary 1 and 0. Sometimes used for telemetry control systems where long cable runs are not required.


Recommended Standard 485. Similar to RS232 but uses a balanced signal mode. A balanced signal mode utilizes a pair of wires where a voltage difference is used to transmit/receive binary information. A balanced voltage signal level travels faster and much longer distances than an unbalanced type. Used extensively for telemetry control systems.

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Sequential Couleur Avec Mmoire (Sequential Color with Memory in English). Color TV system developed in France. Used in parts of Europe, Middle East, Central America and the former USSR.


Signal/Noise Ratio. Measure of noise on a video signal. It is represented in Decibels as the level of the video signal compared to the level of noise present on that signal. The higher the signal to noise ratio the better.


Super Video Home System. An advanced recording system used for tape format. The luminance and chrominance signals are recorded and played back using the two wire Y/C procedure, thus avoiding the degradation experienced when encoding and decoding composite video signals.


Synchronization. Timing pulses that are generated by a camera to identify when a field (complete TV picture) or a line (a single line of a picture) is about to start. These pulses are used to lock the timing of various individual parts of a video system together to prevent 'picture roll' on monitors when switching between different inputs.
Scene Illumination The amount of light (specified in Lux) falling onto a scene that is required to generate a specified video output with a specified lens aperture.
Single Unit Camera All the Power supplies and electronics required to produce the video signal are contained within the camera head. Normally only a power lead and a coax cable need be connected to the camera.

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A system whereby the signals are transmitted between the camera/CCU and a remote control unit. Usually either a twisted pair cable is utilized or the signals are transmitted over a coax cable and superimposed onto the video signal.


Thermo-Luminescent Dosimeter. A small device used to measure radiation.

TV 36

A radiation tolerant underwater cable specifically designed by IST, containing 36 cores of various types specifically for CCTV applications. Includes a Kevlar strength member.


Television Lines - Resolution. The maximum number of changes between light and dark on a picture across the width dictates the resolution of a CCTV camera, measured in TVL.

Twisted pair cable

Screened pair(s) of cores used to transmit control data and balanced video signals. Can also be configured with an integral coax core. Available in LSF or underwater materials.

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Video Home System. A recording system used for tape format. Lately superceded in industry by SVHS.Varifocal Lens (A lens with the facility to manually select between various focal lengths).


A sensor tube using antimony trisulphide for the target layer, (see face plate materials)

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Letter denoting the luminance portion of a video signal.


A method of transmitting the Luminance and Chrominance parts of a color video signal separately down individual wires.

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