DVR

AGC
Automatic Gain Control. When enabled, the camera's sensitivity is automatically increased when the level of ambient light drops.

Aperture
The aperture of a lens controls the amount of light which can reach the pickup device (image sensor when relating to video). The size is controlled by the iris adjustment. By increasing the F-number (F1.2, F1.8, etc), less light will be permitted into the sensor.

ATC
Auto-tracking White Balance. This is a white balance feature that accepts many types of lighting conditions by using an automatic tracking system that automatically controls the color temperature range from 2,400K to 10,000K. ATW mode ensures reliable color reproduction when lighting conditions change frequently.

Auto Iris
Automatic method of varying the size of the lens aperture in response to changes in light.

AWC
Preset White Balance. AWC is suitable where a lot of white objects appear in the scene. Also it is suitable for situations where the object merges into the scene with a similar color shade.

Backlight Compensation
A feature that compensates for bright backgrounds so foreground objects aren't silhouetted.

BNC
Bayonet Nut Connection. Also known as several other names. A connector for coaxial cable that is used in video connections and RG58 connections. The connector has a bayonet-type shell with two small knobs on the female connector which lock into spiral slots in the male connector when twisted on. BNC connections are easily adapted to RCA style jacks and plugs.

Broadband
High speed transmission. Allows for a wide band of frequencies on a single link. Different channels or frequencies within the band can send information concurrently, allowing more information to be transmitted within a short period of time. This allows for access to voice, data, and video all at the same time. DSL and cable TV providers are considered suppliers of downstream broadband.

CCD
Charged Coupled Device. A sensor that collects light and turns it into an electrical signal. As compared to CMOS sensors, it has greater sensitivity to light, better tonal range, and less noise which provides superior quality. CCD will hold onto the high-end CCTV market for some time to come.

CCD Format
The active imaging area of a CCD sensor, measured corner to corner.

CCTV
Closed-Circuit Television

CMOS
Complementary Metal Oxide Semiconductor. A semiconductor fabrication technology that achieves low power dissipation. These types of devices are used in digital camera imaging sensors and consume less energy than other imaging devices, are inexpensive, but provide lower image quality compared to CCD sensors.

Coaxial Cable
The type of cable most commonly used to transmit video.

Compression Techniques
There are several standardized formats for compressing video data. First off, video data needs to be compressed due the enormous amount of data being collected to replicate visual detail and motion. Two fundamental concepts to realize when deciding which video compression technique best suits your needs includes storage consumption and video quality. The most common video compression formats are MJPEG, MPEG-2 (DVD standard), MPEG-4, and Wavelet.

DDNS
Dynamic Domain Name System. Allows for a dynamic or constantly changing IP address to be assigned to a networked device while allowing the associated domain name for that device to remain unchanged. The device in many cases is a server that provides information to clients. While an IP address must be assigned to the server, an optional domain name can be used to identify the device. For example, www.bluenetvideo.com is a server whose IP address is 66.70.185.247. If that IP address changes, DDNS will correctly map the new IP address to www.bluenetvideo.com.

DVMR
Digital Video Multiplexing Recorder. A recorder that gathers and compresses video in a digital format to be saved on a hard drive. A DVMR is much different than a DVR. The DVMR is actually a multiplexing recorder, recording each individual channel in full screen to allow the best possible playback quality. Do to the advances in digital imaging, DVR's and DVMR's have come a long way and are quickly replacing VHS systems.

Digital Recording
Technology that enables images from a camera to be stored on a hard drive. A digital recorder provides clearer images than videotape and faster access to them.

Electronic Shutter
A camera feature that compensates for changes in light conditions, from bright sunlight to dim indoor lighting.

Ethernet
A local area network protocol that operates at OSI layer 2. This protocol is responsible for host to host communication and provides a method of media access for multiple computers to share. In older applications, the shared medium is a coaxial cable (RG8 or RG58 equivalent). Today, we find most applications to utilize a unshielded twisted pair (UTP) cable for connections rather than coaxial. There are several revised additions to the original standard, each describing a method of sharing a single medium with multiple devices. Each standards also specifies the speed at which data can be transferred. For instance, the 10baseT Ethernet cable standard specifies 10Mbit/sec data transfer over twisted pair cable that will not allow a device to transmit and receive data simultaneously. 100baseTX (Fast Ethernet) allows data to be sent and receive simultaneously providing faster data transmission at 100Mbit/sec over twisted pair cable.

Field of View (FOV)
The image area produced by any camera and lens combination (See focal length ) .

Focal Length
The distance from the center of the lens to the point where it focuses light. The combination of focal length and CCD format determines a camera's field of view. The shorter the focal length, the wider the field of view.

Foot-Candle
A unit of illuminates, incident light, or illumination equal to 1 lumen per square foot. This is the illuminants provided by a light source of one candle at a distance of 1 foot, hence the name.

Gain
Gain is an increase or decrease in the strength of an electrical signal.

Lux
A unit measuring the intensity of light. The light of a full moon is about 0.1 lux, while bright sunlight is about 100,000 lux. Basically, the lower the rating the better the camera performs at night. 1.0 lux in video means light level of a candle light. l Lux approximately equals to 10 foot-candles (1 Lux = 10.764 fc).

M-JPEG
Motion Joint Photographic Experts Group. A compression technique for moving images which applies JPEG still image compression to each frame of a moving picture sequence. Playback requires a machine capable of decompressing and displaying each JPEG image quickly enough to sustain the required frame rate of the picture sequence. M-JPEG offers the highest resolution during playback, but is the least efficient in storage.

Multiplexor (Mux)
A device that accepts video signals from a number of cameras and encodes them into one signal that is recorded on a digital recorder or VCR. The multiplexor also decodes the recording, so it can play back motion video from one camera at a time or several cameras all at once to one monitor. Many multiplexors also display several camera views at a time on a monitor while sending images to a recorder.

Noise
Electrical energy or interference that appears on the screen as a grainy picture or "snow".

NTSC
National Television Standards Council. A video format standard used in North America, Japan, and parts of South America.

PAL
Phase Alternating Current. A video format standard used in Europe, Australia, China, etc.

PIR
Passive infrared. A motion detector that senses body heat to detect motion.

PTZ
Pan Tilt Zoom. You will find some video cameras that allow these functions with a series of motors and special housings. Sometimes, you will find units that provide pan and tilt movements only.

Resolution
A measure of the ability of the camera or monitor to reproduce detail. The higher the resolution the clearer the image.

RISC
Reduced Instruction Set Computer. Processors whose design is based on RISC provide a rapid execution of a sequence of simple instructions rather than on the provision of a large variety of complex instructions. This provides for faster decoding and simple addressing modes where more complex modes are replaced by sequences of simple arithmetic instructions.

RJ-45
A serial connector that looks very similar to a standard telephone connector, except that it houses eight wires instead of four.

Switcher
A device that switches views from several cameras to one or more monitors.

S/N (signal-to-noise) Ratio
The ratio between useful video signal and unwanted noise. The higher the number, the better the image quality.

TCP/IP
Transmission Control Protocol / Internet Protocol. This two-layer protocol suite is the foundation for communication on the Internet. Any computer or device that wants to communicate over the Internet must use the TCP/IP protocol stack. TCP provides reliable delivery of information with the ability to correct errors during transmission as well as provide a variety of other reliable features to ensure proper data transfer. IP provides the logical addressing system for any device on a network, ensuring that each unit is identified so communication can take place. Being connectionless, IP treats each individual packet (chunk of data) as a single unit, providing source and destination addresses so each networked device that receives that packet can determine where the packet originated and where it is destined to go. IP does not care whether the information got there or how it got there, that is why TCP and IP must work together. Usually uses a client/server architecture where one device (the client) requests information from another device that supplies the wanted information (the server).

Twisted Pair
A cable composed of two small, insulated conductors twisted together. Since both wires have nearly equal exposure to any interference, unwanted noise is substantially reduced.

Varifocal Lens
A lens that can be manually adjusted for the desired magnification and field of view.

White Balance
A process used in video cameras to retain true colors.