| MAGNIFICATION RATIO | | | | chips. |
| The ratio between the focal length of a lens and the | | | | POLARISING FILTER |
| focal length of a standard angle lens. Indicates the | | | | An optical filter that transmits light in only one |
| magnification of the image when compared to an | | | | direction (perpendicular to the light path), out of |
| image from a standard angle lens. | | | | 360° possible. The effect is such that it can |
| MANUAL IRIS | | | | eliminate some unwanted bright areas or reflections, |
| Type of lens that requires manual focusing. | | | | such as when looking through a glass window. In |
| MATRIX SWITCHER | | | | photography, polarising filters are used very often to |
| Advanced type of switcher in which a signal from | | | | darken a blue sky. |
| any input can be switched to any number or | | | | POTS |
| combination of outputs. Generally used in larger and | | | | Plain Old Telephone Service, ie. the telephone service |
| more complex systems the matrix will usually also | | | | in common use throughout the world today. Also |
| incorporate a range of additional advanced features. | | | | known as PSTN. |
| MICROWAVE TRANSMISSION | | | | PRESET POSITIONING |
| A method of transmitting signals using a microwave | | | | A function of a pan and tilt unit, including the zoom |
| frequency link. Not affected by adverse weather but | | | | lens, where a number of certain viewing positions can |
| requires direct line of site. A licence may be required | | | | be stored in the systems' memory (usually this is in |
| to operate a microwave frequency system. | | | | the PTZ site driver) and recalled when required, |
| MODEM | | | | either upon an alarm trigger, programmed or manual |
| Derived from the term Modulate-Demodulate. A | | | | recall. |
| modem is used to convert between analogue and | | | | PRINCIPLE POINT |
| digital signal to then transmit and receive the signals | | | | An optical term that refers to one of the two points |
| over the PSTN network. | | | | that each lens has along the optical axis. The principle |
| MOIRÉ PATTERN | | | | point closer to the imaging device (CCD chip in our |
| An unwanted effect that appears in the video picture | | | | case) is used as a reference point when measuring |
| when a high frequency pattern is looked at with a | | | | the focal length of a lens. |
| CCD camera that has a pixel pattern close (but | | | | PSTN |
| lower) to the object pattern. | | | | Public Switched Telephone Network usually refers to |
| MULTIPLEX VIDEO RECORDING | | | | the "plain old telephone" service. Also known as |
| The condensed recording of more than one video | | | | POTS. |
| signal on a single videotape, or hard disk drive. | | | | PTZ SITE DRIVER |
| MULTIPLEX | | | | (PTZ site receiver, or decoder). An electronic device, |
| The concept of transmitting several signals on a | | | | usually a part of a video matrix switcher, which |
| single channel. | | | | receives digital, encoded control signals in order to |
| MULTIPLEXER | | | | operate pan, tilt, zoom and focus functions. |
| A device that combines a number of signals into one. | | | | QUAD COMPRESSOR |
| Often used in CCTV to describe a device that is | | | | (Also split screen unit). Equipment which |
| primarily used to multiplex several video signals into | | | | simultaneously displays parts or more than one image |
| one for the purposes of recording or microwave | | | | on a single monitor. It usually refers to four quadrants |
| transmission. It can also refer to a fibre optics | | | | display. |
| multiplexer which combines a number of video signals | | | | RAID |
| into one in order to transmit all of them via a single | | | | Redundant Arrays of Independent Disks. This a |
| fibre cable. | | | | technology of connecting a number of hard drives |
| N/C AND N/O ALARMS | | | | into one mass storage device, which can be used, |
| Refers to Normally Closed and Normally Opened | | | | among other things, for digital recording of video |
| contacts. It is usually used to describe alarms in | | | | images. |
| CCTV. | | | | RAM |
| NA | | | | Random Access Memory. An electronic chip, usually |
| Numerical Aperture. A measure of the angular | | | | known as "memory", holding digital information while |
| acceptance of light incoming into a fibre optics cable, | | | | there is power applied to it. Its capacity is measured |
| in the form of a cone. It is expressed as the square | | | | in kilobytes. |
| root of the difference of the squares of the indices | | | | RANDOM INTERLACE |
| of the core and the cladding. | | | | A term describing a camera that has a free running |
| NBS | | | | horizontal sync as opposed to a 2:1 interlace type |
| National Bureau of Standards (USA). | | | | which has the sync locked and therefore has both |
| ND FILTERS | | | | fields in a frame interlocked together accurately. |
| Neutral Density filters are optical filters that attenuate | | | | REMOTE CONTROL |
| the light a number of times. This attenuation is equal | | | | A transmission and receiving of signals for controlling |
| for all the wavelengths therefore it does not change | | | | remote devices such as pan and tilt units, lens |
| the colour balance of an image, hence the term | | | | functions, wash and wipe control and similar. |
| neutral. | | | | RETMA |
| NIT | | | | Former name of the EIA association. Some older |
| A photometric unit for measuring luminance. One nit is | | | | video test charts carry the name "RETMA Chart". |
| equal to one candela per square metre of a | | | | RF SIGNAL |
| projected surface area. | | | | Radio frequency signal that belongs to the region up |
| NOISE | | | | to 300GHz. |
| An unwanted signal produced by all electrical circuits | | | | RG-11 |
| working above the absolute zero. Noise cannot be | | | | A video coaxial cable with 75 Ohms impedance and |
| eliminated but only minimised. | | | | much thicker diameter than the popular RG-59 (of |
| NTSC | | | | approximately 12 mm). With RG-11 much longer |
| National Television System Committee, an American | | | | distances can be achieved (at least twice the RG-59), |
| committee that set the standards for colour | | | | but it is more expensive and harder to work with. |
| television as used today in USA, Canada, Japan and a | | | | RG-58 |
| few other countries. | | | | A coaxial cable designed with 50 Ohms impedance, |
| O/P | | | | therefore not suitable for CCTV. Very similar to |
| Output. Objective. The very first optical element at | | | | RG-59, only slightly thinner. |
| the front of a lens. | | | | RG-59 |
| OCULAR | | | | A type of coaxial cable that is most common in use |
| The very last optical element at the back of a lens | | | | in small to medium size CCTV systems. It is designed |
| (the one closer to the CCD chip). | | | | with an impedance of 75 Ohms. It has an outer |
| OSCILLOSCOPE | | | | diameter of around 6 mm and it is a good |
| (Also CRO, from "Cathode Ray Oscilloscope"). An | | | | compromise between maximum distances achievable |
| electronic device that can measure the signal changes | | | | (up to 300 m for monochrome signal, and 250 m for |
| versus time. A must for any CCTV technician. | | | | colour) and good transmission. |
| PAL | | | | RMS |
| Stands for Phase Alternating Line, which describes | | | | An abbreviation for Root Mean Square. All AC |
| the colour phase change in a PAL colour signal. | | | | voltages are measured with multimeters that show |
| PAN AND TILT HEAD | | | | the RMS value of the signal (not the peaks). For a |
| (P/T head). A motorised unit permitting vertical and | | | | sine wave signal such as the mains, the RMS value |
| horizontal positioning of a camera and lens | | | | happens to be 1.41 times (square root of 2) below |
| combination. Usually 24 VAC motors are used in such | | | | the peak values. |
| P/T heads, but also 110 VAC, ie. 240 VAC units can | | | | ROM |
| be ordered. | | | | Read Only Memory. An electronic chip, containing |
| PAN UNIT | | | | digital information that does not disappear when |
| A motorised unit permitting horizontal positioning of a | | | | power is turned off. |
| camera. | | | | RS-232 |
| PHOT | | | | A format of digital communication where only two |
| A photometric light unit for very strong illumination | | | | wires are required. It is also known as a serial data |
| levels. One phot is equal to 10,000 luxes. | | | | communication. The RS-232 standard defines a |
| PHOTODIODE | | | | scheme for asynchronous communications, but it |
| A type of semiconductor device in which a PN | | | | does not define how the data should be represented |
| junction diode acts as a photo sensor. | | | | by the bits, ie. it does not define the overall message |
| PHOTO-EFFECT | | | | format and protocol. It is very often used in CCTV |
| Also known as photoelectric effect. This refers to a | | | | communications between keyboards and matrix |
| phenomenon of ejection of electrons from a metal | | | | switchers, or between matrix switchers and PTZ site |
| whose surface is exposed to light. Photon. A | | | | drivers. The advantage of RS-232 over others is in |
| representative of the quantum nature of light. It is | | | | its simplicity and use of only two wires. |
| considered as the smallest unit of light. | | | | RS-422 |
| PHOTOPIC VISION | | | | This is an advanced format of digital communication |
| The range of light intensities, from 105 lux down to | | | | when compared to RS-232. The basic difference is in |
| nearly 10-2 lux, detectable by the human eye. | | | | the need for four wires instead of two as the |
| PINHOLE LENS | | | | communications is not single-ended as with RS-232, |
| A fixed focal length lens, for viewing through a very | | | | but differential. In simple terms, the signal transmitted |
| small aperture, used in discrete surveillance situations. | | | | is "read" at the receiving end as the difference |
| The lens normally has no focusing control but offers | | | | between the two wires without common earth. So if |
| a choice of iris functions. | | | | there is noise induced along the line, it will be |
| PIXEL | | | | cancelled out. The RS-422 can drive lines of over a |
| Derived from picture element. Usually refers to the | | | | kilometre in length and distribute data to up to 10 |
| CCD chip unit picture cell. It consists of a photo | | | | receivers. |
| sensor plus its associated control gates. | | | | RS-485 |
| PLUMBICON | | | | This is an advanced format of digital communications |
| Thermionic vacuum tube developed by Philips, using a | | | | compared to RS-422. The major improvement is in |
| lead oxide photoconductive layer. It represented the | | | | the number of receivers that can be driven with this |
| ultimate imaging device up to the introduction of CCD | | | | format, and this is up to 32. |