"C" mount/"CS" mount: CCTV lenses come in two different lens mounts. The "C-mount" lenses have a flange back distance of 17.5mm vs. 12.5mm for "CS-mount" lenses. C-mount lenses can be used on CS-mount cameras by utilizing a 5mm adapter or adjusting the camera for C-mount lenses. Because of the shorter back focal distance, CS-mount lenses can only be used on CS-mount cameras. CS-mount lens cannot be used on a C-mount camera. Most CCTV cameras accept either C or CS-mount lenses.

CCD. (Charged Coupled Device): A CCD is an electronic chip that is the receiving device on a camera. Sony CCDs are the most popular and largest share of CCD market

CCTV: The common abbreviation for Closed Circuit Television. The common term for a “closed” video system or one that is used for the specific purpose as to not broadcast and is typically used for video security and surveillance.

Candlepower: The unit measure of a light intensity.

COAXIAL CABLE: A type of cable capable of passing a range of frequencies with low loss. It consists of a hollow metallic shield in which one or more center conductors are put in place and isolated from one another and from the shield. Common conductor material is copper and aluminum is used in cheaper coax cable. Siamese coax is coax cable with a pair of wires for camera power.

Composite: video The combined video signal that includes the picture signal, the vertical and horizontal blanking and synchronizing pulses. It is a simple two-wire connection that is commonly used in video monitors and monitor output on DVRs.

Crosstalk: An undesired signal or noise that interferes with the signal.

Database: A collection of data used and produced by a computer program.

DB (Decibel): A measure of the power ratio of two signals. A unit used to express relative difference in power or intensity, usually between two acoustic or electric signals, equal to ten times the common logarithm of the ratio of the two levels.

DC TYPE lens: An auto-iris lens with internal circuitry that receives the video signal from the camera to adjust the iris. Common Auto-Iris lens

Default Gateway: The IP Address of the Router that is used to send information from one network to another.

Depth of field: The front to back zone in a field of view which is in focus in the picture scene. With a greater depth of field, more of the scene, near to far, is in focus. Increasing the f-stop number increases the depth of field of the lens. The lens aperture should be set at the highest f-stop number usable with the available lighting. The better the lighting, the greater the depth of field possible. The depth of field is the area in front of the camera which remains in focus. The larger the f-number the greater is the depth of field.

Digital Recording: This is the latest form of recording and is relatively new to the CCTV industry as a result is not the most economical method however it does have several advantages over the VCR analogue tape recorders. First of all it enables quick access to the desired

Duplex (multiplexer): A multiplexer that allows the user to look at multi-screen images while performing time multiplex recording.

Dwell Time: The length of time a monitor or DVR maintains a view on a given camera before moving on to the next view. Many DVRs will rotate between views based on alarms and the dwell time allows a specified time to view each screen before it is refreshed

E.I. (Electronic Iris): Automatically changes a CCD camera¹s shutter to mimic Auto Iris control, allowing fixed or manual iris lenses to be used in a range of areas that used to require an auto iris lens. Not as efficient as Auto-Iris lenses and cameras

Electronic shuttering: Electronic shuttering is the ability of the camera to compensate for moderate light changes in indoor applications without the use of auto iris lenses.

Ethernet: A type of LAN connection and protocol that is recognized as an industry standard. Used on most all IP networks