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Picture of Darren Shurmer (admin)

Darren Shurmer (admin)

Dotted Decimal Notation

Dotted Decimal Notation is the representation of a binary IP address in decimal format, separating each octet with a period or dot.


DS0 is the basic digital signaling rate. DS stands for Digital Signal, and is a system of classifying digital circuits according to the rate and format of the signal. A DS0 offers 64 Kbps of bandwidth - the amount of bandwidth usually used for one telephone voice channel.

DS1 Signal

DS1 signal is the signal or logical bit pattern carried on a T1 line and is the equivalent of 24 DS0s or channels.


see Digital Source Master

Dual-light System

The dual-light system offers effective surveillance and crime deterrence with a combination of IR and white-light illuminators. When darkness falls, the cameras on-board infrared (IR) illuminator switches on automatically to capture clear black and white images. Then if there is movement within its field of view, the camera automatically triggers its integrated white LED illuminator, bathing the immediate scene in light; the illuminator can also be spotted clearly from far away. The illuminators sudden switch-on also provides a powerful visual warning to unexpected visitors. At the same time, the camera switches automatically to colour video mode, capturing detail-packed images in colour to assist with positive identification of the subject.

Dynamic Ports or Private Ports

Dynamic Ports or Private Ports are software ports in the range 49,152 to 65,535 and the Internet Assigned Numbers Authority does not manage them. Randomly chosen port numbers in this range are referred to as ephemeral ports. These ports are not permanently assigned to any publicly defined application and are commonly used as the source port number for the client side of a connection. This allocation is temporary and is valid for the duration of the connection opened by the application using the protocols.


The Defog Image Processing feature is capable of clearing up fog, mist, and haze in a scene to achieve images that are more visible.

E1 Line

E1 is a dedicated copper telephone line that supports data rates of 2.05 Mbps. An E1 line operates at Layer 1 or the Physical layer and is commonly available world-wide with the exception of North America and Japan where T1 lines are used. An E1 line consists of 32 individual channels or DS0s, each of which supports 64 Kbps. Each channel or DS0 can transport voice or data. A customer can lease an entire E1 line or only a few channels, which is known as fractional E1 service.

E3 Line

E3 is a dedicated copper telephone line that supports data rates of 34.37 Mbps and like an E1, is also built on the base DS0 signal. An E3 is 16 E1s-or 512 DS0s-bundled together.

Easy Focus

Focus adjustments can be performed using the Easy Focus button built in our cameras for easy installation. These adjustments can also be made from a PC.

Easy Zoom

Zoom ratio adjustments can be performed using the Easy Zoom button built in our cameras for easy installation. These adjustments can also be made from a PC.

Edge Storage (on-board recording with memory cards)

The Edge Storage function records video and audio data with memory cards (such as SD and micro SD cards) attached to the camera. It can be used for fail-over data backup if the network is disconnected due to unstable network conditions or other difficulties. It can also be used for event recording when the recording is started by an alarm signal triggered by the cameras video analytics functions (such as Intelligent Motion Detection and Tamper Alarm), as well as by user-defined rules of DEPA and DEPA Advanced technologies. This function also enables scheduled recording, for convenient local storage. The recorded data can be transmitted to network video recorders (NVR)/video management software (VMS) and merged with data saved on the NVR/VMS storage. SD cards capable of an Edge Storage Maintenance Notification function* are recommended for these applications. * Memory cards have a finite lifespan that is reduced over time by recording. With the Edge Storage Maintenance Notification function, users can obtain remotely the lifespan information of cards attached to the camera.

Electronic D/N

Electronic D/N is a technology to make the image more visible in low-light conditions by removing the chroma or colour signal to produce a B/W image.

Electronic Image Stabilizer

Electronic Image Stabilizer electronically compensates for movement in captured images using image processing. Two images captured back and forth by the camera are recorded to its buffer memory, in which the cameras image processor calculates their distance and compensates for movement. This helps to minimize the effect of camera shake or vibration and achieve less blurry images.


Ethernet is the most common set of rules controlling network communications for local area networks. It is a set of standards that define rules such as frame format as well as how computers communicate with each other over a single wired shared by all devices on the network. These rules give any new device attached to the wire the ability to communicate with any other attached device. Ethernet can also be used as a wide area network (WAN) technology. In this application, it is often referred to as carrier Ethernet. Organizations such as the Metro Ethernet Forum are helping to accelerate adoption of carrier Ethernet networks and services.

Ethernet Cabling

Ethernet cabling is twisted-pair cabling that meets standards for use on an Ethernet-based network. Category 5 (Cat 5) and Category 5e (Cat 5e) cabling are commonly in use today. Straight through Ethernet cables can be used to connect an end-user device to a networking device such as a switch. Crossover Ethernet cables can be used to connect one end-user device directly to another.


The e-Varifocal feature allows the installer to adjust the fixed-lens cameras field of view in a similar way to adjusting the field of view on a varifocal lens camera at installation. The fixed-lens camera maintains the selected resolution, while also allowing digital zoom, pan and tilt operation to fine tune the angle of view. After installation, precise adjustments can be made to the fixed-lens cameras field of view. This can be done on a remote basis, reducing the cost of maintenance.

Evidence Shot

Evidence Shot records high-quality JPEG images with the cameras maximum resolution at a low frame rate, simultaneously providing an overview video stream with smaller size images in H.264. This function is useful for applications where forensic analysis is required to identify faces and car license plates in city streets and car parks. The high resolution (20 megapixels with the SNC-VM772R) allows for enlargement of specific areas of interest in the scene to examine details more precisely.

Extension Headers

In IPv6, extension headers are used to extend the functionality of the IPv6 header. IPv6 has a fixed length header. Optional extension headers are then used to extend functionality when needed. The IPv6 header and each extension header contain a Next Header field, which specifies the type of the next header that follows. This allows a variable number of extension headers to be added.

Fiber Distributed Data Interface (FDDI)

Fiber Distributed Data Interface (FDDI) is a standard for data transmission on fiber optic lines that can extend in range up to 200 km (124 miles).

Fiber Optic Lines

Fiber optic lines are glass or plastic threads or fibers used to transmit data. Fiber optic lines operate at Layer 1 or the Physical Layer. SONET/SDH connections use fiber optic lines.


See Forensic Mark


Federal Information Processing Standards. All DCI compliant projection systems must be inside cases complying to the FIPS-140 standard. This prevents physical access to the movie by unauthorised personnel

Five-Layer Reference Model

The Five-Layer Reference Model is a commonly used combination of the OSI Reference Model and the TCP/IP Reference Model. The five layers defined in this model are as follows: Application Layer,Transport Layer/Layer 4, Network Layer/Layer 3, Data Link Layer/Layer 2, Physical Layer/Layer 1


Cinema language for 1.85:1 picture aspect ratio. Close to 16:9 format

Flicker Reduction

Flicker Reduction minimizes flicker phenomena that are seen as blinks or horizontal stripes caused by differences in brightness on the monitor when shooting video under fluorescent, sodium, or mercury lamps. This function analyses brightness of the captured images and compensates for differences in brightness with image processing to maintain picture quality with fewer flickers.


For a switch or bridge, flooding means forwarding data on of all ports except the port on which data was received. When one of these network devices receives data destined for an unknown address, data destined for the broadcast address, or data destined for a multicast address, it will flood the data on all of its ports except for the port on which the data was received.

Forensic Marking

A signal which is encoded within the picture/audio that is invisible to the human eye/ear. If the movie is copied with a camcorder/stills camera (audio recorder), the pirate copy/still picture/audio can be analysed to extract the forensic mark which will tell which cinema the movie was copied in

Forward Explicit Congestion Notification (FECN)

Forward Explicit Congestion Notification (FECN) bits are bits in the Frame Relay header used to notify an end station, such as a router, of network congestion. When congestion occurs, Frame Relay switches set the FECN bit to a 1 in frames going toward the destination location or going downstream. In this way, all downstream devices learn about congestion.

Forwarding Equivalency Class (FEC)

A Forwarding Equivalency Class (FEC) is a group of packets that the provider's MPLS domain forwards and treats the same.

Forwarding Storm

A forwarding storm is network congestion caused by a looped network. When a bridge or switch receives a frame for which it doesn't have the destination MAC address in its table, or when it receives broadcast or multicast traffic, it floods the frame out every other port. In a looped network, this can result in the same data being received on multiple ports and being forwarded again and again. A forwarding storm can block all other network traffic and bring a network to a complete stand still. To prevent loops, bridges and switches can use the Spanning Tree Protocol, or STP.

Forwarding Table/MAC Address Table

A forwarding table or MAC address table is where a switch stores address and location information for all devices connected directly to its ports.


Fragmentation is the process of breaking an IP packet into smaller chunks or fragments when transmitted over data link technology with a smaller MTU.


A frame is one unit of data encapsulated at Layer 2, or the Data Link Layer. Each frame is divided into three parts: the header, the data, and the trailer. The frame header contains the data's destination and source Layer 2 addresses. It also indicates which Layer 3 protocol should be used to process the data on the receiving computer. (In the examples in this course, the IP protocol is used.) The frame trailer is a checksum, which is used to verify data integrity.

Frame Check Sequence (FCS)

Frame Check Sequence (FCS) is a 2-byte or 4-byte checksum computed over the frame to provide basic protection against errors in transmission.

Frame rate

The number of frames of a moving image that can be transmitted per a second.

Frame Relay

Frame Relay is a Layer 2 WAN protocol used to interconnect multiple locations or LANs over a single communications line-such as a T1/T3 or E1/E3 line. With this single line, customers can communicate with multiple sites using virtual circuits. Frame Relay is a cost-effective alternative to dedicated point-to-point connections and can be used to build a Layer 2 Virtual Private Network.


File Transfer Protocol (FTP) is a network protocol used to transfer data from one computer to another through a network, such as over the Internet.

FTP client

Software to be used for accessing the FTP server.

FTP server

A server to be used to transfer files via a network.

Full Duplex

Full-duplex data transmission allows for communication in two directions at the same time. That is, a device can receive and transmit data simultaneously. This functionality is similar to using a telephone where you can talk and listen at the same time.

Global Routing Prefix

In an IPv6 address, the global routing prefix is the first part of the network prefix, and is followed by a subnet ID. The global routing prefix is typically assigned by an ISP or regional address allocation entity.

Greenfield Preamble

A Greenfield preamble is used in 802.11n to indicate to communication devices the beginning of a new frame. In an environment that has no legacy devices, using the Greenfield preamble can increase throughput because it is shorter than a legacy preamble. However, in mixed environments, both preambles must be used.


One of the image compression formats. The standard written by the JVT (Joint Video Team) , joint organization for standardization composed of ISO and ITU-T. H.264 is capable of transmitting video data at a higher compression rate than that of MPEG4.

Half Duplex

Half-duplex data transmission allows for communication in two directions, but only in one direction at a time. That is, a device cannot receive and transmit data simultaneously. This functionality is simlar to using a walkie talkie where if you are speaking, you cannot hear the person on the other end.

Handshake or Three-way Handshake

A handshake or three-way handshake is the three-step process two devices go through to establish a connection before they can communicate.

Hardware Ports

SeeNetwork Interface Card (NIC)


See High Definition


The hexadecimal numbering system is a base 16 numbering system, in contrast to the commonly used base 10 decimal numbering system. In the hexadecimal numbering system, the digits 0 through 9 are used the same as they are in decimal numbering. After that, the letters A through F are used to represent the decimal number 10 through 15. For instance, decimal 15 is hexadecimal F and decimal 16 is hexadecimal 10.

Hidden Node Problem

In wireless networks, the hidden node problem occurs when there are two clients on either side of an access point which are within range of the access point, but which can't actually hear each other's transmissions. In this situation both clients may simultaneously transmit data, resulting in collisions at the access point, which is unable to interpret either signal.

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