Mostly Asked CCTV Camera/ Device Installer Interview Preparation Guide

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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.

This is a feature of security cameras that automatically adjusts the image to compensate for bright light to give more detail on the darker areas of the image. For example, use is to focus on the detail of a face of a person that has the sunlight shining from behind.

A type of cable typically used in cctv installations that has a central conductor, surrounded by a shield sharing the same axis. The shield can be made from a variety of materials including, braided copper, or lapped foil. There are various standards for specific types of co-axial cable. The cable used for normal CCTV installations is called RG59.

IP waterproof ratings are a BSi standard measurement for how waterproof something is. Many security cameras or camera housings are designed for outdoor use need to be waterproof. The IP rating number has two digits, and optional letters after them. E.G IP66 and IP68. The first number defines the protection against ingress of foreign objects. 0 is the lowest rating and means non-protected. 6 is the highest rating and means dust tight and protects against access with a wire. The second number defines the level of protection against ingress of water. 0 is the lowest rating means non-protected. 8 is the higest rating and means protects against continuous immersion in water.

PAL is an abbreviation for Phase Alternating Line. This is the television display standard that is used mainly in Europe, China, Malaysia, Australia, New Zealand, the Middle East, parts of Africa, and other parts of the world. PAL uses 625 lines per frame and a frame rate of 25 frames per second.

RS485, also referred to as EIA-485 is a communications standard for serial communication between devices. When talking about surveillance systems, RS-485 is typically used as the protocal to allow computers and remote controllers to control the activity of cameras such as pan, tilt, rotate, and zoom operations. RS485 is an updated version of the original serial protocol, RS-232.

All of the technologies allow you to see your cameras from your phone. You just have to download the right app for it.

Some DVRs and security cameras have alarm inputs, which can accept input from a sensor device such as a door contact or a passive infra-red motion detection which trigger the camera or DVR to take some action such as to begin recording.

The length of time a switcher or CCTV multiplexer displays one camera before sequencing to the next. Multiplexers with dwell time programming capability allow you control this length of time.

Connecting an additional device in parallel with an existing video cable. For example, when driving a video recorder as well as a monitor from the same video signal.

This is a type of lens with a very small aperture. Normally used for covert applications, where it can easily hide behind or within another object.

Technology used for flat screen displays.

Digital video pictures can be compressed with a number of techniques. These include: JPEG and JPEG-2000 (for still images), M-JPEG and MPEG (for moving pictures).

Devices with internal sync have an internal crystal to provide sync pulses without needing reference from any external device.

This is a measure of the resolution of a video device. The higher the number, the higher the resolution is. 380 TVL is considered medium resolution. 480 TVL or greater is considered high resolution.

A method of displaying set-up information and/or instructions on a display monitor.