A Digital Video Recorder is a generic term for a device that is similar to a VCR but records television data in digital on a hard drive as opposed to a VCR tape. A DVR looks like a VCR and has all of the same functionality of VCR (recording, playback, fast forwarding, rewinding, and pausing) plus the ability to skip to any part of the program without having to rewind or fast forward the data stream.
This refers to a camera that is designed to record pictures and transmit them directly over a computer network or internet connection. Network cameras normally do not have any analogue video outputs. The images are encoded directly in one of the standard compression techniques, such as JPEG or MPEG.
NTSC is an abbreviation for the National Television Standards Committee. The term "NTSC video" refers to the video standard defined by the committee, which has a specifically limited color gamut, is interlaced, and is approximately 720 x 480 pixels, and 30 frames per second (fps). This standard is used in North America.
Unit of light illuminance used as a measure of low-light recording capacity in security cameras. Cameras with a Lux rating of 0.2 Lux or less would be considered low-light cameras. It is not possible to get good color definition in low light levels, so in general low light cameras are always black and white. Day/night cameras use electronics to switch from color during the daytime, to black/white during night or low light conditions. Many low light cameras also use infrared, which is useful in zero light conditions. The lower the LUX rating of a camera, the better it will see in low light.
JPEG is a standard for the encoding and compression of images. JPEG is used in the video surveillance systems to compress and store individual frames of video. JPEG was developed by the Joint Photographic Experts Group.
Security cameras with auto iris, have the ability to compensate for large variations in light levels. This is useful for security cameras that need to adjust for changes from bright sunlight to darkness or night. Auto iris circuitry is normally linked to a motorized drive that opens and shuts the iris on the camera lens. Closing a physical iris is a much better way to protect a camera from being damaged by bright sunlight then simply using electronics to reduce the signal strength.
There are two main types of lenses used in security cameras. The C mount lens has a flange back distance of 17.5mm. The CS mount lens has a flange back distance of 12.5mm. C mount lenses therefore have a longer focal distance. CS mount became widely used, because it its more practical for many of today's more compact cameras. Lenses are often supplied with a 5mm spacer ring (sometimes called a C ring) that allows a C mount lens to be used on a CS camera. Most modern security cameras are CS.
The encoded output of a surveillance camera whereby the red, green, and blue video signals are combined with the synchronizing, blanking, and color burst signals and are transmitted simultaneously down one cable.
The opening of the CCTV lens. The size of which is controlled by the iris and is measured in F numbers. Generally, the lower the F number, the larger the aperture is and consequently more light can pass through the lens.
A device that forwards data packets along networks. Typically when referred to in CCTV installations, a router is used to connect a surveillance DVR and a computer to a single internet connection. A router can also be used to connect multiple IP based security cameras to a single internet connection.