A.G.C. (Automatic Gain Control).

An electronic circuit that tries to keep signals at a constant level; more useful in cameras at low light levels. The higher the number the better; typical values 12 - 20dB, i.e. a gain of approx 4x - 10x.

A.I. (Auto Iris).

An electronic circuit fitted to the iris of a lens to help compensate for large changes in light levels.

A.L.C. (Automatic Level Control).

On A.I. lenses, also known as the peak/average control. Adjusting this control allows the auto iris circuitry to either take bright spots more into consideration (peak), bringing out detail in bright areas, or less into consideration (average) bringing out detail in shadows.

Access Authorisation.

Permission granted to a card number enabling the cardholder to enter a location based on a programmed time schedule.

Activity Detection.

A feature of the Generation 3 video multiplexer range that uses video motion detection techniques to improve the camera update times. It also gives a relay closure.

A.D.S.L. (Asymmetrical Digital Subscriber Line).

A telephone line with uneven transmission rates; half the transmission can attain speeds up to 640 kbps; the other half can attain speeds of 2.048 Mbps or greater in the opposite direction.

Ah.

Ampere hours, e.g. 1A for 6 hours = 6Ah. Always de-rate the battery capacity by 66%.

A.I.T. (also seed.D.S.3/D.D.S.4) (Advanced Intelligent Tape).

First generation tape drive that will replace D.D.S. technology. A.I.T. has several advantages over D.D.S. drive range: 30,000 tape passes; regular head cleaning not required; larger memory capacity - 20Gb or 35Gb native. An in-built memory chip (M.I.C.) to increase the speed of data searches.

A.I.T.2.

Second generation "Advanced Intelligent Tape" drives, with a larger memory capacity of 50Gb native.

Alarm Bypass Relay.

A relay in the controller that is used to shunt or bypass the door alarm contacts of a central alarm system to allow authorised access without causing an alarm.

Alarming.

The ability of C.C.T.V. equipment to respond to an input signal, normally a simple switch closure. The response varies depending on equipment type; most common is for switcher to ‘hold’ on the camera corresponding to the alarm input.

Ambient.

Light Level Background or general light level of a given area.

Analogue.

A signal in which any level is represented by a directly proportional voltage; not digital.

Angle of View.

This is what alters (not the focal length) when you use a lens designed for one format on another format. It decreases with format size.

Anti-Passback.

An arrangement where the software flags a card as either 'in' or 'out' when it is used at designated readers. Anti-passback can be either local or global, i.e. per controller or per system. Anti-passback can also be timed.

Aperture.

The ‘opening’ of a lens, a measure of its light gathering capability. Relative Aperture is a ratio between its focal length and effective aperture, measured in F numbers, generally the lower the better.

Archive.

Long-term storage of digital files to a removable media. At this time HARD DRIVE RAID DISK is the most common media for archiving of digital recordings.

Aspherical Lens.

A lens designed with a non spherical shape so that it refracts the light passing through it to either lower the lens aperture so that it passes more light or decrease barrel distortion on wide angle lenses.

Asynchronous Transmission.

Transmission in which time intervals between transmitted characters may be of unequal length. Transmission is controlled by start and stop bits at the beginning and end of each character. Compare with synchronous transmission.

A.T.M. (Asynchronous Transfer Mode).

A high-speed cell-switching network technology that handles data and real-time voice and video. A.T.M. is defined in the Broadband I.S.D.N. (B.I.S.D.N.) standard and provides "bandwidth on demand" by charging customers for the amount of data they send. Data rates are scalable, starting as low as 2.048 Mbps with intermediate speeds of 25,51 and 100 Mbps, to high speeds of 155,622 Mbps and up into the gigabit range.

Auto White Balance.

Feature on colour cameras whereby the camera constantly monitors the light and adjusts its colour to maintain white areas.

Auto-terminating.

Feature whereby the equipment automatically selects the correct termination depending on whether the video output B.N.C. is connected.

B. Channel. (Bearerchannel).

A 64-kbps I.S.D.N. user channel that carries digital data or a P.C.M. encoded digital voice.

B.I.O.S. (Basic Input/Output System).

The part of a computer’s operating system that handles the flow of data between software and hardware. For example, a program’s request to save a file to disk goes through the B.I.O.S.

B.L.C. (Back Light Compensation).

A feature of modern C.C.D. cameras which electronically compensates for high background lighting to give detail which would normally be silhouetted.

Back Focus.

The mechanical aligning of the imaging device with the focal point of the lens. Most important on zoom lenses to ensure the image stays in focus throughout the zoom range.

Balanced Signal.

Method of transmitting video, usually over twisted pair cable that consists of two equal but opposite signals being sent down two conductors.

Balun. (Balanced Unbalanced).

A device that connects a balanced line, such as twisted pair, to an unbalanced line, such as coax cable.

Band Width.

The frequency range that an electronic circuit can accept.

Bandwidth.

The range of frequencies available for signalling the difference between the highest and lowest frequencies of a band, measured in Hertz.

Base-Band Video.

Unmodulated video signal suitable for display on a monitor but not a domestic T.V.

Baseband.

A full-channel bandwidth transmission where digital signals are placed onto a transmission line with no change in their modulation.

Baud Unit of signalling speed.

The speed in baud is the number of line changes (in frequency, amplitude) or events per second. At low speeds, each event represents only one bit condition, and baud rate equals b.p.s. As speed increases, each event represents more than one bit and baud rate does not truly equal b.p.s.

Baud rate.

Data transmission speed.

Bit. (Binary Digit).

The smallest unit of information in a binary system; a one or zero condition.

Black Level.

The level on a video signal, just above the sync pulses, where black portions of the picture are represented.

Blanking. (Field and line flyback blanking).

The operation of turning off the monitor display, or pick-up device, during sync pulses to avoid thin white lines appearing on the picture.

B.N.C. Video connector.

The most commonly used connector in C.C.T.V.

B.R.I. (Basic Rate Interface).

An I.S.D.N. service referred to as 2B+D, B.R.I. provides two 64-kbps bearer digital channels plus a 16-kbps delta channel. I.S.D.N. terminal adaptors replace moderns as the customer-premise connection to this service for direct connections of data and voice transmissions.

Bridge.

A device that connects two L.A.N. segments together, which may be of similar or dissimilar types, such as Ethernet and Token Ring.

Byte.

A unit of information, usually shorter than a computer "word." Eight-bit bytes are most common. Also called a "character." Category 1 through 5 cables (CAT 1-5) The following categories are based on their transmission capacity. Categories 1 through 5e are based on the TIA/EIA-568 standard. Cable type application; 1 UTP Analogue Voice, 2 UTP Digital Voice, 1-Mbps Data, 3 UTP, STP 16-Mbps Data, 4 UTP, STP 20-Mbps Data, 5 5e UTP STP 100-Mbps Data

C Mount.

Long established industrial standard for connecting cameras and lenses, widely used in the C.C.T.V. industry.

C.C.D. (Charged Coupled Device).

A ‘chip’ that performs the same function as a camera tube.

C.C.I.R. (Comite Consultatif International Radiocommunications).

The European T.V. standard 625 lines 50 fields.

Cable screen/shield.

A conductor which forms a sheath around one or more insulated conductors. This reduces the effect of interference onto the conductors. This shield is usually metallic foil or stranded wire wrapped around the conductors.

Card Number.

Coded number stored in the access control card.

Card Reader.

Unit fitted by the controlled door that reads the access card and transfers the information to the access control system.

Cardholder.

An individual who has been issued an access control card.

C.C.T.V.

Short name for Closed Circuit Television.

C.D.-R.O.M. (Compact Disc Read-Only Memory).

A compact disk format used to hold text, graphics and hi-fi stereo in excess of 650 MB of data, which is equivalent to about 250,000 pages of text or 20,000 medium-resolution pages.

Chrominance (C).

The part of the video signal corresponding to the colour information.

Co-Axial Cable.

Any cable that has a conductor and shield sharing the same axis.

Composite Sync.

A signal comprising of both Line and Field sync pulses but without any video information.

Composite Video.

The full video signal, including both video data and sync pulses.

Compression.

A number of methods to reduce the size of digital information. See J-PEG, M-PEG and Wavelets.

Conditional Refresh.

Technique used in slow and fast scan where only small screen changes are transmitted. Up to a certain percentage of the on-screen picture can be updated before a full picture is required.

Controlled Area.

A location where entry and/or exit is under the control of other persons or a control system. An area where the entrance and exits are controlled by an access control system is a controlled area.

C.S. Mount (Special C. mount).

New standard for connecting cameras and lenses. It has a shorter penetration into the camera, needed for many modern C.C.D. designs.

C.S. to C. Mount.

Adaptor 5mm spacer ring used to enable the use of C. mount lenses on C.S. mount cameras.

D. Channel (Delta Channel).

This 16-kbps channel is used to signal the telephone company computer to make calls, put them on hold and activate features such as conference calling and call forwarding. It also receives information about incoming calls, as in Caller ID. May also be used for low-speed transactions with x.25 protocol.

D.D. (Direct Drive).

An Auto Iris lens requiring a D.C. reference from the camera rather than the traditional video reference.

Daisy chain.

To connect devices in a series, one after the other where the transmitted signals go to the first device, then to the second and so on.

D.A.T./D.A.T. Drive (Digital Audio Tape).

Despite its name this is currently the most popular method for long term storage of any digital data.

Data cable.

Cable used for transmitting low level signals between system units.

dB (decibel).

A logarithmic unit for comparing two voltages, each 6dB doubles the voltage.

D.D.S.3.

The third generation "Digital Data Storage" tape drive system. Used to archive the digitally compressed pictures from many hard disk video recorders, 12Gb native memory. Specified at 1,000 tape passes (recommended VHS tape use is 10 passes for security applications). The main draw back with this technology for security use is the drives need for frequent head cleaning.

D.D.S.4.

The fourth generation "Digital Data Storage" tape drive system, 20Gb native memory. Specified at 1,000 tape passes. The main draw back with this technology for security use is the drives need frequent head cleaning.

Default.

An assumption made by the system when no specific choice is given by the programme or the user.

Depth of Field.

The area of acceptable focus of an image. The wider you set the aperture of a lens the lower the depth of field becomes.

Dialup Line.

A two way line used in Public Switched Telephone Network (P.S.T.N.).

Digital.

A signal that levels are represented by binary numbers. These can be kept in a store.

D.V.R. (Digital Video Recorder).

See Hard Disk Recorder.

Distribution Amplifier.

A device that accepts a video signal and sends it out over a number of independent outputs.

Distribution Code.

A code allocated to each Cotag distributor to ensure security. Only cards carrying this code will work with the system supplied by your distributor.

Dome Camera.

A camera housed in a dome shaped mounting. Dome cameras can be either static looking at a fixed point, or movable on a pan tilt and zoom axis.

Door Open Time.

The time allowed for a controlled door to remain open after a valid entry before raising an alarm on the system.

Door Strike.

An electro-mechanical device used to lock and unlock a door under electrical control.

D.O.S.

A disk operating system in which programmes are stored on disk.

Dry Contact.

A contact that is isolated or unconnected from any electrical source.

Duplex (Multiplexer).

A multiplexer with two frame stores allowing it to show multi-screen pictures while performing time multiplex recording.

D.V.D. (Digital Video Disk, Digital Versatile Disk).

A standard agreed on by the computer, consumer electronics and entertainment industries for storing 4.7 or more GB of data on a single optical disc the size of a C.D.

D.V.R.

The standard name for digital video recorder.

Dwell Time.

The length of time a switcher will hold a camera before moving on to the next in sequence.

E.I. (Electronic Iris).

Automatically varies a C.C.D. camera’s shutter to mimic Auto Iris control, allowing fixed or manual iris lenses to be used in a wider range of areas.

Echelon.

Operating protocol that is used in the Sprintdome control system.

E.I.A. (Electronic Industries Association).

A standards organisation in the U.S. specialising in the electrical and functional characteristics of interface equipment.

Encoded.

The result of transferring information in a coded form to a medium.

Ethernet.

A local area network (L.A.N.) developed by Xerox, Digital Equipment Corp. and Intel.
Standardised as IEEE 802.3 and ISO 8802.3. Ethernet connects up to 1024 nodes at 10 Mbps over twisted pair, coax and fibre optic cable. When a station is ready to send, it transmits its data packets onto the network, which is common to all nodes. All stations "hear" the data. The station that matches the destination address in the packet responds while the others do nothing. Ethernet is a data-link protocol and functions at the Physical and Data-link Levels of the O.S.I. model (Layers 1 and 2).

Ethernet Address.

A unique 48-bit number maintained by the IEEE/ISO and assigned to each Ethernet network adaptor.

Event.

Valid transactions reported by Access Control and Monitoring Systems.

Exit.

Refers to a way out of an area which may or not be controlled.

Ext. Sync (external sync).

The ability of C.C.T.V. equipment, normally cameras, to accept one or more of the standard sync formats so as to align itself to the rest of the system.

EXview™.

The latest interline C.C.D. sensor from SONY that has increased sensitivity across the visible spectrum and the near I.R.

Fail Locked (Fail Secure).

Locking device requiring current to unlock.

Fail Unlocked (Failsafe).

Locking device requiring current to lock.

Fast Ethernet.

Generally refers to 100BASE-T and 100BASE-FX but may also include 100VG.

Field.

One half of a frame, consisting of either the odd or the even numbered lines, 50 fields are transmitted every second.

Field of View.

The view achieved with a particular lens; varies with the focal length.

File.

The orderly arrangement of data or information.

Firewall.

A network node set up as a boundary to prevent unauthorised traffic from one segment to cross over to another. Firewalls are used to improve network traffic, as well as for security purposes.

Flash memory.

A memory chip that holds its content without power but must be erased in fixed blocks rather than single bytes. Block sizes typically range from 512 bytes up to 256KB.

Focal Length of a lens.

The distance in millimetres, between its secondary principal point and its focal point. The higher the number the greater the magnification and the less the field of view.

Focal Point.

The point on the axis of a lens to which parallel rays of light will cover.

Format.

How the computer arranges the information onto disk. Can also apply to printers.

Frame.

One complete TV picture made up of approximately 625 lines. 25 frames are transmitted every second.

Frame Relay Packet.

Switched network similar to X.25 but with end-to-end error-checking and high-speed transmission rates.

Frame Store.

Digital information store capable of holding a complete frame of video information.

Frame Transfer.

C.C.D. type of C.C.D. chip which consists of vertical charge transfer channels placed side by side. During vertical blanking, the charge generated in the light sensitive imaging area is rapidly transferred into a shielded storage area. During the horizontal blanking, this charge is shifted down a line at a time into a horizontal shift register where it is clocked out during each line period to form the video signal.

Full Picture Update.

The technology which enables a transmission system to update a high quality full picture on each picture refresh at very fast speeds.

Galvanometric(galvometric).

One method of converting the small electric currents produced by Auto Iris circuits into physical movement of the iris diaphragm. Used in both Auto Iris and Direct Drive lenses.

Gamma.

A camera adjustment that ensures a linear correlation of light gain on the entire system eg. A doubling of light input gives double light output.

Gateway.

A computer that performs protocol conversation between different types of networks or applications.

Gen. Lock (see ext. sync.).

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

Gigabit.

Ethernet Technology that adapts the Ethernet model for data transmission at 1 Gbps or higher.

Gigabyte (Gb).

Order of magnitude; 10 9.

Ground Loop.

An unwanted continuous or temporary ground current flowing back and forth between two devices that are at different ground potentials.

Hall effect.

A type of door monitoring built into magnetic locks.

Hard Disk.

Non volatile digital data storage device used in PCs. Come in various storage sizes, normally measured in giga-bytes. See Hard Disk Recorder.

H.D.R. (Hard Disk Recorder or Digital Video Recorder – D.V.R.).

Device that uses digital techniques to record CCTV pictures to a hard disk. The results can be of higher quality than V.H.S. or S.V.H.S., events can be found faster and there is no loss of quality when copies are made.

Hardwired.

Method of controlling camera points using multicore cable.

Holiday Code.

A V.C.R. timer feature that allows you to assign the Sunday timer settings to up to 20 weekdays per year. Normally used for Bank holidays.

Hot Swapping.

Removing and replacing a component of a larger system while the system is receiving power and operating.

H.T.M.L. (Hyper Text Mark-up Language).

A standard for defining documents with hypertext links. H.T.M.L. is a subset of S.G.M.L. (Standard Generalised Mark-up Language) and is used to establish links between documents on the World Wide Web.

H.T.T.P. (Hyper Text Transfer Protocol).

The clients/server protocol used for connections to servers on the World Wide Web. Addresses of Web sites begin with an http://prefix.

Hub.

A central connecting device in a network that joins communications lines together in a star configuration.

Hz (Hertz).

Cycles per second.

I.R. (Infra Red).

A range of frequencies lower than visible red light used for covert surveillance or as a low cost wireless video link.

Ident.

Number or title super-imposed on a video signal.

id-visual.

Company with extensive knowledge in security design and installation.

Image Sensor.

Format Size of the C.C.D. element in the camera.

Impedance.

The effective resistance of an electronic circuit to an A.C. signal.

Interlace (2:1interlace).

The accurate combining of two fields, one odd one even, into a single frame.

Interleaving.

Method used with alarms or activity detection which allows extra frames of video from alarmed cameras to be added to a time multiplexed sequence whilst a state of alarm exists.

Interline Transfer.

C.C.D. type of C.C.D. chip in which the photosensors acquire and store an electric charge according to the intensity of light falling on them. The charges are first transferred to a vertical shift register and then a horizontal shift register. This is controlled by an external pulse timing system.

Internal Sync. (crystal controlled).

A camera that generates its sync pulses without reference to any other source. Normally using a crystal controlled oscillator.

Internet.

1) Any large network made up of several smaller networks.
2) A group of networks that is interconnected so that they appear to be one continuous large network and can be addressed seamlessly at the O.S.I. Network layer through routers.
3) The industry name for the Worldwide interconnected network. Based upon the original ARPANET network, it’s used as a reference resource, a way of sending e-mail and an online chat room for users around the world.

Intranet.

A network connecting a related set of standard Internet protocols and files in H.T.M.L. format with employees using Internet browsers in an organisation’s network and within the corporate firewalls.

I.P. (Internet Protocol).

The protocol used in gateways to connect networks at the O.S.I. Network Layer (Layer 3) and above. I.P. routes a message across networks.

Iris (Iris diaphragm).

Adjustable diaphragm that regulates the amount of light passing through a lens.

I.S.D.N. (Integrated Services Digital Network).

A digital switched network used to transmit voice, data, images or video. Also see B.R.I.

J-PEG (Joint Picture Expert Group).

A popular suite of digital compression tools. Originally for use with "still" pictures but often used in C.C.T.V. products.

Kb.

Kilobyte or one thousand bytes or characters of information. Kilo Order of magnitude; 10 3.

L.C.D. (Liquid Crystal Display).

A type of flat screen display.

Leasing.

A method of funding a project over an agreed payment term.

Leased Line.

A telephone line reserved for the exclusive use of leasing customers without interexchange switching arrangements. Should not be mistaken for private line that is owned by the user over private property.

Lens Calculator Software.

A computer program for specifying correct lenses.

Lens Calculator.

Wheel used for calculating a lens size or distance from a camera to the subject.

Line Amplifier (Video line corrector).

A device to make good the loss of signal strength and quality due to long cable runs.

Line Fed Camera.

A camera that receives its power along the same cable that is used to send its picture back to the monitor.

Line Lock.

To synchronize the field sync pulses, of an AC powered camera, to the frequency of the voltage input (line voltage).

Linux.

A freeware, clone version of the UNIX‚ System V release 3.0 kernel that runs on PC x86 machines and other platforms.

LAN (Local Area Network).

A data-communications system confined to a limited geographic area (up to about 10km) with moderate to high data rates (100 kbps to 100 Mbps). The area served may consist of a single building, a cluster of buildings or a campus-type arrangement. The network uses some type of switching technology and does not use common carrier circuits (although it may have gateways or bridges to other public or private networks)

Looping.

Video input of a piece of video equipment both unterminated and including the relevant sockets for the extra coaxial cables.

Luminance (Y).

The part of a video signal that consists of the monochrome data.

Lux.

Metric measure of the light striking a surface. The light available from that surface will depend on how reflective it is.

M-P.E.G. (Moving Picture Expert Group).

A suite of digital compression tools specifically designed to video images.

M.A.C. (Media Access Control).

The protocol that controls access to the physical transmission medium on a L.A.N.

Macro.

Feature allowing you to pre-programme frequent system configurations for selection by a single keystroke or optionally by alarm inputs.

Magnetically Encoded.

Coded information that has been recorded on magnetic tape or cards.

Matrix Switcher.

A switcher able to route any of its camera inputs to any of its monitor outputs; a name usually reserved for large systems that often includes telemetry control.

Mb.

Megabyte, or one million bytes or characters of information.

Modem.

Used with P.S.T.N. telephone lines to connect a fast scan system to the dial up BT network.

Modem (Modulator-Demodulator).

A device used to convert serial digital data from a transmitting terminal to an analogue signal (carrier) for transmission over a telephone channel or to reconvert the transmitted analogue signal to serial digital data for acceptance by a receiving terminal.

Monitored.

Senses the state of the door (i.e. open or closed), a door contact is usually used.

Monochrome.

Black and white, not colour.

Mullion.

Door frame side uprights. (Mullion reader – a reader designed to be mounted on the door frame).

Multimode Fibre.

An optical fibre with a core diameter of 50 to 100 microns. Its core causes some distortion and provides less bandwidth than single-mode fibre.

Multiplex (Time multiplex).

Using one carrier to send more than one signal. In video multiplexers, achieving this by sending a different camera’s output in each successive field or frame of a video signal, in a form that can later be retrieved as single camera pictures.

Multiplexer.

A device that divides a transmission into two or more sub-channels, either by splitting the frequency band into narrow bands (frequency division) or by allotting a common channel to several transmitting devices, one at a time (time division).

N.T.S.C. (National Television Standards Committee see E.I.A.).

Colour T.V. system used in the U.S.A.

N/D (Neutral Density).

A filter that attenuates light equally over the whole visible spectrum.

Nano.

Order of magnitude; 10 –9

Native.

The raw memory capacity of a given media. The memory capacity of tapes is often specified including the tape drives 2:1 compression capabilities. i.e. a 12Gb native tape will be specified as 24Gb etc. Digital hard disk recorders cannot use the tape drives 2:1 compression capabilities.

Network.

A series of points connected by communications channels.

N.I.C. (Network Interface Card).

Board that provides network communication capabilities to and from a computer system. Also called an adaptor.

Noise.

Unwanted signals present on data lines.

Null Modem.

A device that connects two D.T.E.s directly by emulating the physical connections of a D.C.E.

Off-line.

Access control system not connected to a central computer.

On-line.

Access control system connected to a central computer.

One stop solution.

A complete solution for all your electronic security systems.

O.S.D. (On-Screen Display).

The ability of a camera or a piece of camera control equipment to display its set-up menu on a display monitor. Thereby greatly simplifying installation.

O.S.I. (Open System Interconnection).

An architectural model developed by the I.S.O. for the design of open systems networks. All communication functions are divided into seven standardised layers: Physical, Data Link, Network, Transport, Session, Presentation and Application.

P-P (Peak-to-Peak).

The voltage of a signal measured between its most positive and negative points. C.C.I.R. standard video is 1 volt P-P.

P.A.L. (Phase Alternate Line see C.C.I.R.).

Colour T.V. system used in the U.K.

P.A.B.X. (Private Automatic Branch Exchange).

An in-house telephone switching system that interconnects telephone extensions to each other, as well as to the outside telephone network.

Password.

A special word, code or symbol that must be presented to the computer system to gain access to its resources. It identifies the user to the computer system.

P.C.I. (Peripheral Component Interconnect).

Bus P.C.I. Local Bus is a high-performance bus that provides a processor- independent data path between the C.P.U. and high-speed peripherals. P.C.I. is a robust interconnect mechanism designed specifically to accommodate multiple high-performance peripherals for graphics, full-motion video, S.C.S.I. and L.A.N.s.

P.C.M.C.I.A. (Personal Computer Memory Card International Association).

A non-profit trade association founded in 1989 to standardise a method for connecting peripherals to P.C.s. P.C.M.C.I.A. created a 16- bit socket that’s "Plug-and-Play" compatible and can be automatically configured by a software driver called P.C.M.C.I.A. Card Services.

Peak White Inverter (Eclipser).

An electronic circuit that turns any white part of a video signal, over a preset level, to black. If installed in the auto iris video line it decreases the contrast of one picture, bringing out detail otherwise lost in shadow.

Pedestal.

The portion of a video signal between the sync. pulses and the black level.

Peer-to-Peer.

Communications in which both sides have equal responsibility for initiating, maintaining and terminating the session.

Phase Adjustable (see line lock).

The ability to delay the line locking process, so as to align cameras fed from A.C. voltages on different phases.

Photocell.

Automatically switches on the infra-red lights when light levels fall to a preset level.

Pico.

Order of magnitude; 10 –12

P.I.N.

Personal Identification Number.

P.I.N.G. (Packet Internet Groper).

A utility used to determine if a T.C.P./I.P. device is available and responsive on a network or at an Internet site.

P.L.259/U.H.F. Connector.

Screw on video connector, now largely replaced by the B.N.C. type.

Plasma.

A type of flat screen display.

Port.

That portion of a computer through which a peripheral device may communicate.

P.O.T.S. (Plain old telephone service).

The basic analogue service provided by the public telephone network, without any added facilities.

P.P.P. (Point-To-Point Protocol).

A data-link protocol that provides dialup access over serial lines by encapsulating protocols in specialised Network Control Protocol packets. These packets can be used to replace a network adaptor driver which allows remote users to log on to the network as if they were in-house.

Presets.

The pre-positioning of pan, tilt and zoom cameras by the use of potentiometers in the moving parts of the camera head. These allow the control equipment to store and move to a set reference point when the controller dictates or when an alarm exists. Special telemetry equipment is required.

Protocol.

A standard for sending coded messages between computers and peripherals.

Protocol Converter.

Data transmission converter i.e. RS232 to RS485 or vice versa.

Proximity.

Radio frequency technology used in Access Control, where the card or tag needs to be presented to a reader. Read ranges vary but are not normally greater than 15cms.

P.S.T.N. (Public Switched Telephone Network).

By switching communication system- such as Telex, T.W.X. or public telephone networks-that provides circuit switching to many customers.

P.S.U.

Power supply unit.

Pulse.

A positive or negative change in voltage that conveys information to a circuit.

P.V.P.™ (Parallel Video Processing).

Multiplexer dual frame store that gives near real-time record capability in 3 hour mode and improves multi-screen updates by 50%.

Quad Splitter.

Device that uses digital techniques to compress four full pictures onto one monitor screen.

Rack Mount (19" rack).

An industrial standard housing 19" wide, its height is measured in units (U’s) of 1.75".

Redwall.

An external motion detector used in the C.C.T.V. industry.

Remote Access Server.

A computer or self-contained unit that provides remote dial up access to a L.A.N. through modems and/or I.S.D.N. adaptors.

Remote Set-up.

(Protos3 Cameras) The ability to set-up the cameras operational features, with the ease of O.S.D., from a Baxall compatible via co-axial telemetry transmitters, without the need for telemetry receiver. No extra cabling is required.

Router.

A system that stores and forwards data packets- by way of network addresses- from one L.A.N. to W.A.N. to another.

RS-422.

E.I.A. interface standard that generally operates in conjunction with RS-449 and specifies electrical characteristics for balanced circuits and extends transmission speeds and distances beyond.

RS-232/V.24.

RS-422 is a balanced voltage system with a high level of noise immunity.

RS-485.

Balanced interface similar to RS-422/V.11 but using tri-state drivers for multi-drop applications.

RS232.

A data communication industry standard for the serial transmission of information. Distance without modems is limited.

RS485.

A data communication industry standard for transmission of information.

Rugby Clock.

Radio signal to synchronize equipment clocks accurately and that automatically adjusts the BST setting.

S-V.H.S. (Super Video Home System).

New format high resolution V.H.S. video recorders, capable of giving greatly improved picture if all features are used. V.H.S. compatible.

S-V.H.S.+.

A recording system that can playback a picture with a resolution of over 410 T.V.L.

S.E.C.A.M. (Systeme Electronique Couleur Avec Memoire).

Colour T.V. system used in France.

S/N Ratio (Signal to Noise Ratio).

Measure of noise levels of a video signal; the higher the number the better.

Scanner.

A pan only unit.

SCART.

Standard European 20 pin connector used for carrying both video and audio signals in domestic T.V. appliances now utilised on some C.C.T.V. equipment.

S.C.S.I. (Small Computer Standard Interface).

A hardware bus interface that enables a single expansion board in the computer to be connected to up to 7 or 15 peripheral devices (hard disk, CD-ROM, Scanner, etc)

Secondary code.

Part of the security code stored in the access card which identifies the installation the card belongs to.

Serial Transmission.

Method of data transmission in which the bits of a data character are transmitted sequentially over a single channel.

Short-Haul Modem.

A data Communications Equipment (D.C.E.) device that amplifies and conditions the data signal for transmission over cable for long distances.

Shutter.

An electronic circuit available on many C.C.D. cameras. Allowing the light gathering period (1/50th of a second) of the camera to be stopped prematurely (as little as 100,000 of a second).

Simplex (Multiplexer).

A multiplexer with 1 frame store that can either time multiplex records or show multi-screen pictures in live or play back. It cannot record the multiplexer pictures whilst showing multi-screen pictures.

Single-Mode Fibre.

An optical fibre that supports only one mode of light propagation above the cut off wavelength. The core diameters are usually between 5 and 10 micrometres (um).

Swivel Mount.

Used on a tower or bracket to enable the housing to be pointed at any angle, vertically or horizontally.

Sync (Synchronisation pulses).

Pulses generated, normally by the camera, to tell other pieces of equipment when a picture (field sync) or one line of a picture (line sync) is to start.

Telemetry.

A system utilising ‘control code’ transmitters and receivers. These use the video cable or a simple twisted pair cable to send their information.

Terminated (75 Ohm terminated).

Video input of a piece of C.C.T.V. equipment, wired to be the last in a particular video line.

T.F.T. (Thin Film Translator).

A type of flat screen display.

Time Zone.

A period of time during which access is authorised. It can be defined by the time of day and days of the week.

Time-Lapse.

V.C.R. Video recorder that can record frames with pauses between them thereby extending the time that a standard length tape will last.

T.B.C. (Time Base Corrector.)

Electronic circuit that aligns unsynchronised video signals before signal processing. Used in multiplexers and quad splitters.

Token Ring.

A network-access mechanism and ring topology in which a supervisory frame or token is passed from station to station as a poll for network transmission (IEEE 802.5 standard).

Triplex™.

Multiplexer feature that gives you the ability to simultaneously view both playback and live cameras within the same multi-screen, while still encoding.

T.V.L. (Television Lines - Resolution).

The maximum number of changes between light and dark on a picture across 3/4 of the width dictates the resolution of a C.C.T.V. product, measured in T.V.L.

Twisted Pair.

A cable, often screened, that consists of two conductors twisted together along their length.

UNIX.

An operating system originally designed by AT&T for multi-users applications. Other versions include AIX, XENIX and LINUX.

Unlock time.

Refers to the time that the system holds the door locking device energised to allow entry or exit.

Unmonitored.

Does not sense the open/closed state of the door.

Unterminated Hi-Z.

Video input of a piece of C.C.T.V. equipment, wired so as to allow the video signal to be fed to further equipment. Does not necessarily include extra sockets for the extra coaxial cables.

Update Rate.

The number of pictures (fields) per second recorded by time-lapse VCRs/Multiplexers or H.D.R.s.

U.S.B. (Universal Serial Bus).

Serial 4-wire bus architecture for peripherals I/O ports; autosenses up to 128 peripherals at a distance of 5 metres and at a maximum data rate of 12 Mbps.

User Friendly.

The term applied to software and/or hardware that has been designed to be used easily without having to remember complex procedures.

V.B.S. (Video Burst Sync.).

A composite colour video signal.

V.H.S. (Video Home System).

Name given to 1/2" tape format domestic video recorder.

V.S. (Video Sync).

A composite monochrome video signal.

Varifocal.

A type of lens which enables a manual selection between two focal lengths to give the desired picture view.

Vertical Interval Switching.

Sequential switchers waiting until the current field has finished before they display the next camera, even though the dwell time has elapsed.

VEXT.

A multiplexer feature that uses a pulse generated by the V.C.R. so that the multiplexer automatically adjusts to the V.C.R. time lapse speed.

V.M.D. (Video Motion Detection).

A system that uses the video signal from a camera to determine if there is any movement in the picture and set off an alarm.

V.L.A.N. (Virtual L.A.N.).

Devices on a L.A.N. or L.A.N.s that are configured for communications as if they were attached to the same wire, when in reality they are located on a number of different L.A.N. segments.

V.X.A.

Cost effective digital tape media.

W.A.N. (Wide Area Network).

A data-communications network spread across a wide geographic area and incorporating a large number of users. A WAN often uses transmission devices provided by common carriers. Examples of WANs include Frame Relay, S.M.D.S. and X.25.

Wiegand.

Originally a high security card and reader system using the properties of a unique alloy wire to produce a binary number. Now used more frequently to describe readers and controllers using Wiegand format data.

Windows.

Graphical user interface.