Alternating Current Adapter; when plugged to AC Power (usually 117VAC/60Hz in the United States) it produces 12VDC, 24VAC or others. "UL Listed" and "Regulated" recommended. It is also called Power Transformer.
12VDC
Most board cameras, mini cameras and about one third of the professional cameras work with 12V DC 100mA to 200mA for B/W cameras and 150mA to 300mA for color ones.
24VAC
About two thirds of the professional cameras work with 24VAC, 20VA to 40VA. The cameras usually have screw type connections and you don't need to worry about the polarity. This power is usually supplied with AC Adapter and you need to prepare separate power cable for the connection. Unlike 12VDC, this power can be transmitted to a long distance up to 450ft and is proper for the cameras that are to be installed out-door or when you don't have the power outlet near the camera.
The number of hertz (cycles per second) showing the difference between the lower and upper frequencies of a frequency band Video uses higher frequency than audio, thus requires a wider bandwidth.
BLC
According to special area of measuring light and adjust the electrical shutter, the exposal value will be normal in the measuring area.
Complementary - Metal Oxide Semiconductor A video image sensor chip that produces much lower quality picture than CCD chip
Camera Sensors
Video image sensor
CCD or C-MOS chip
<More details>
CCD (charge coupled device) consists of several hundred thousand individual picture elements (pixels) on a tiny 1/2", 1/3", or 1/4" chip. Each pixel responds to light falling on it by storing a tiny charge of electricity. The pixels are arranged on a precise grid, with vertical and horizontal transfer registers carrying the signals to the camera's video processing circuitry. This transfer of signals occurs sixty times per second. The 1/3" CCD chip is the most widely used sensor format these days; its size is 5.5mm (diagonal), 4.4mm (horizontal) and 3.3mm (vertical). The 1/4" sensor format, recently being used in color cameras, is 4mm (diagonal), 3.2mm (horizontal) and 2.4mm (vertical).
C-MOS (Complementary - Metal Oxide Semiconductor) chip, also a video image sensor, produces much lower quality picture than CCD chip
CCD
Charge Coupled Device. A video image sensor chip
CCD (charge coupled device) consists of several hundred thousand individual picture elements (pixels) on a tiny 1/2", 1/3", or 1/4" chip. Each pixel responds to light falling on it by storing a tiny charge of electricity. The pixels are arranged on a precise grid, with vertical and horizontal transfer registers carrying the signals to the camera's video processing circuitry. This transfer of signals occurs sixty times per second. The 1/3" CCD chip is the most widely used sensor format these days; its size is 5.5mm (diagonal), 4.4mm (horizontal) and 3.3mm (vertical). The 1/4" sensor format, recently being used in color cameras, is 4mm (diagonal), 3.2mm (horizontal) and 2.4mm (vertical).
CCTV Closed Circuit Television
It does not broadcast TV signals but transmits them over a closed circuit through electrically conducting cable or wireless transmitter and receiver.
<More details>
CCTV, Closed Circuit Television, is a TV system that does not broadcast TV signals to public but transmits them over to limited monitor(s). CCTV system usually utilizes CCD video cameras (to produce the video), cable or wireless transmitters/receivers or Internet (to transmit the video), and monitors (to see the video). CCTV system is not only applied to the security and surveillance purpose but also to the other fields like laboratory in schools or in private companies, even to production lines in factories. As the application of CCTV system increased, the CCTV industry has developed variety of CCTV equipment like Time Lapse VCRs, combiners, infrared illuminators, Pan/Tilt, etc. The most recent development is web camera server that uses the Internet for remote surveillance
CCTV Camera A part of the CCTV system that captures the video pictures.
CCTV Monitor part of the CCTV system that receives the video pictures from a CCTV camera and displays them.
<More details>
B/W Monitor and Color Monitor
In the past, 9 to 12 inch (diagonal) B/W monitors were widely used in the field. These days, many people are looking for 14 inches for color monitor and 17 inches for B/W. As the color monitor needs 3 different color dots to produce one pixel of information on the monitor, it usually has lower resolution than B/W monitor.
Single Monitor, Quad Monitor and 4-Ch. Monitor
Single Monitor is usually professional monitor with one video input of BNC jack. Quad splitter, video switcher or multiplexer can be connected to single monitor to combine multiple cameras. Quad monitor has built-in quad splitter and usually has 4 DIN jacks for video inputs. 4-Ch. Monitor has built-in 4 channel video switcher and usually has 4 DIN jacks for video inputs. Quad Monitor or 4-Ch. Monitor is usually a part of packaged observation system and is not compatible with other manufacturer's camera or cable.
Direct Current Power; can be derived from an AC adapter or from a battery. Among DC voltages of 6, 9, 12, 24, 28, 12VDC is most common in the CCTV industry.
<12VDC>
Most board cameras, mini cameras and about one third of the professional cameras work with 12V DC, 100mA to 200mA for B/W cameras and 150mA to 300mA for color ones. These cameras usually have DC jacks to accept DC power plugs. You should be careful about the polarity (positive and negative) for this power source. 12V DC power can be supplied with AC Adapter or battery pack. You may even
DVR Digital Video Recorder records video pictures digitally. DVR, Digital Video Recorder, records video pictures digitally on a hard disk drive(HDD). This HDD, usually built-in, has capacity of 20 Gb, 30 Gb or 60Gb to store the records. You can program the picture resolution and recording time according to the application; real-time or time-lapse recording also available. Overwriting the oldest pictures is programmable. Event alarm recording that records, only when a movement is captured within the image frame, is easier to program and more reliable than the Time Lapse VCR's alarm recording function. You just assign dots over the screen where you want to detect the movement. As DVR records digitally, the image quality remains the same regardless of how many times the images are stored or rerecorded. And, you can select images quickly by using time/date or alarm search, or just browsing through.
Electronic Shutter, one of the major features of CCD camera, is not really a moving shutter, but a clever piece of signal processing.
Under low light conditions, the CCD is allowed to gather signal at the electronic shutter speed of full 1/60th of a second.
Under brighter lighting conditions, the video processing chip automatically responds by reading the CCD and then immediately "early purging" it, resulting in precise control over the video level. Even at a shutter speed of 1/100,000th of a second, the CCD camera is still delivering 60 images per second, but each image is gathered over a much shorter period of time. The end result is a fantastic picture, with no fading, no adjustments, and best of all, unbelievable reliability.
The Radio Corporation of America; conveniently used to describe phono jack and plug, one of the audio/video connectors.
Resolution Expressed by TV lines or pixels, it indicates the quality level of video images.
<Camera Resolution>
The industry of CCD video camera sensor uses pixels (picture elements) as its quality parameter. Medium resolution of B/W camera in EIA system is 510 horizontal pixels by 492 vertical pixels and is equivalent to 380 TV lines. High resolution is 768(H) x 492(V) pixels and equivalent to 570 TV lines. Color camera's medium resolution means 330TV lines and high resolution needs more than 460 TV lines.
<Monitor Resolution>
The monitors in NTSC system have 525 vertical scanning lines regardless of their size. The horizontal 700 TV lines of B/W monitors represents medium level and more than 900 TV lines means high resolution in EIA system. The color monitor's horizontal resolution of 300 TV lines means medium quality and that of more than 450 TV lines means high resolution.
Sensitivity can be quoted in two different ways.
a) Usable picture
Sometimes this is called minimum illumination. This gives merely an indication of minimum light level at which the camera start providing an output video signal.
b) Full video
This is the real value to be taken into consideration as it gives the lowest light value at which camera supplies a full output video signal "1V peak to peak". This value is important for the whole CCTV system because many devices need a full signal to operate properly.
Sensitivity can be measured:
a) At the faceplate
In this way, it measures the camera performance when all light falls directly on the sensor faceplate. Although this is a technically correct figure, it never actually happens, because to get a real picture you need a lens, which reduces in some ways the light amount falling on the faceplate.
b) At the lens
This is a more effective value of the actual sensitivity of the camera + lens system. Obviously the lower is the F-No the better result you get
<For Instance>
A camera having a value of 0.1Lux (full video) with f1.4 lens has a higher sensitivity than a camera showing the same value of 0.1Lux with f1.2 lens. By using f1.2 lens with the 1st camera its sensitivity would be possibly around 0.08Lux. Another value to be taken into consideration is the scene reflectance (which is the light amount, in percentage, reflected by the scene).
The higher is the reflectance value, the higher is the light amount available to the camera faceplate. Usually the reflectance is something between 65% and 90%.
<For Instance>
A camera having a sensitivity of 0.1Lux (full video) with a f1.2 lens with a reflectance value of 70% is more sensitive than a camera having the same sensitivity (full video) with the same lens but at 90%.
The sensitivity value is normally specified in ‘Lux'. However some American manufacturers give this value in foot-candle. 1Lux = 10fc.
S/N ratio signal/noise ratio It is a measure showing the amount of interference caused by noise. Its value is important especially at low light values. The higher its value, the better will be the picture quality at low light levels.
(1)CCIR is made the technical recommendation for the European 625 line standard for video signals.
(2)EIA is American standard for B/W camera system.
2..PAL/NTSC is for color system.
PAL is a color television system, which is used in Europe, Australia , parts of Africa and the Middle East . It has 625 horizontal scan lines and 25 frames per second. (Frame: A whole video image; is composed of two interlaced fields. A CCD chip produces 30 frames per second at NTSC system and 25 frames at PAL. )
NTSC formulates standards for American color television system. NTSC system has 525 horizontal scan lines and 30 frames per second.
A device that accepts signals from a video camera/microphone and records
video/audio on magnetic tape in a cassette The VCR can play back recorded
video/audio on a television set or CCTV monitor.
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