CCTV SYSTEMS CCTV MONITORS
CCTV SYSTEMS • A monitor simply allows remote viewing of cameras in a CCTV system from a control room or other location. • A video monitor should have a resolution that is at least as good as the camera’s resolution if not better.
CCTV SYSTEMS • There is a saying that a surveillance system is only as good as its monitor. • There is another saying that a surveillance system is only as good as it’s cameras. • There is yet another saying that a surveillance system is only as good as the installer…
CCTV SYSTEMS • Recent advances in technology ensure that a customer can purchase a high quality system. • There are two types of security monitors: the older, bulky CRT monitor and the newer, sleeker LCD monitor. • The CRT monitor can be B/W or color, LCDs are color only.
CCTV SYSTEMS • CRT stands for Cathode Ray Tube. • It is the traditional box type of monitor or television. • The inside of a CRT monitor consists of three phosphor layers, one each for red, green, and blue colors.
CCTV SYSTEMS • When these layers are hit with electron beams, energy from the electrons is converted into light radiation, different compositions of the phosphor create different colors.
CCTV SYSTEMS • LCD stands for Liquid Crystal Display and it is actually not new. • It was first introduced in 1970 but for a long time it was inferior in image quality. • The inside of an LCD monitor consists of a liquid suspended between two glass or plastic panels.
CCTV SYSTEMS • The liquid crystals are naturally aligned to let light pass through except for when a current is applied, In this case, it blocks light, turning the affected area dark. • Different amounts of light are made to pass through the crystals by altering the amount of current used. • Red, green, and blue chambers inside the monitor produce color when varying amounts of current is passed through these chambers.
CCTV SYSTEMS • LCDs provide better image quality than CRTsthey produce a sharper, brighter picture because they can process CCTV signals at a higher resolution. • These monitors are also more responsive than CRTs, making them ideal for live video monitoring. • They are much lighter and less bulky than CRT monitors so they take up much less room.
CCTV SYSTEMS • LCDs also come in large sizes for multiple camera viewing situations. • A big advantage of CCTV LCDs over CRTs is that LCDs do not suffer from magnetic interference.
CCTV SYSTEMS • Speakers, for example, do not need to be shielded to be used in conjunction with the monitor. • Another advantage of a CCTV LCD is screen flicker is not an issue. • With CRT monitors, low refresh rates leads to screen flicker, an annoying occurrence.
CCTV SYSTEMS • Despite all these advantages, there are some disadvantages to a CCTV LCD, One is the contrast ratio. • It is easier to produce higher contrast in CRT monitors because the electron gun can be turned off for true blacks. • In an LCD the backlight is always on so a certain amount of light will always show through, Because of this, buyers should be aware of an LCD monitor’s contrast ratio,an effective ratio is 400:1.
CCTV SYSTEMS • Another drawback is LCD monitors sometimes generate dead pixels, or areas of the screen that remain black because they no longer function. • If the monitor is under warranty, most manufacturers will repair dead pixels, but this leads to system downtime.
CCTV SYSTEMS • An important distinction should be made between CCTV LCD monitors and regular LCD monitors. • CCTV LCD monitors have a processing scaler, which is a device designed to display the best possible picture from a security camera by up converting the signal. • CCTV LCD monitors can cost as much as two to three times more than a regular LCD monitor.
CCTV SYSTEMS • The viewing angle is a limiting factor of LCD monitors. • LCDs typically come with VGA, HDMI, composite and BNC connections as well as audio connections.
CCTV SYSTEMS • It should be noted that any time we use the word monitor it means there is no TV tuner in it. • Monitors, both CRT and LCDs have controls for contrast, brightness etc., on CRTs the adjustment knobs are on the monitor, for LCDs it is an on screen menu.
CCTV SYSTEMS • Monochrome CRT monitors are typically deployed in CCTV systems over color CRTs. • Monochrome is considered a better choice because of it’s clarity and resolution, monochrome is not the same as black and white. • Monochrome is one color and the absence of that color.
CCTV SYSTEMS • Monitor sizes are measured diagonally, CRT monitors have an aspect ratio of 4:3and LCDs monitors are typically 16:9 which is the widescreen standard.
CCTV SYSTEMS • All CRT’s use the NTSC (National TV standards committee) standard which is the analog standard. • LCDs use the ATSC (Advanced TV systems committee) which is the digital standard, most LCDs also support the NTSC standard. • Most CRT monitors will also support the PAL (Phase Alternating Line) European standard.
CCTV SYSTEMS • Another thing to consider is the TVL (television lines) of the CRT monitors. • TVL is a standard used by cameras as well. • 450 TVL and below is considered a standard resolution where approximately 500 TVL is closer to be a HD (high definition) standard.
CCTV SYSTEMS • LCD monitors will support all TVL standards however resolution for flat screens are 720P, 1080i and 1080P. CAN YOU TELL THE DIFFERENCE? 1080i 1080P
CCTV SYSTEMS • What does the “I” and the “P” in 1080i and 1080P stand for? THE “i” STANDS FOR INTERLACED AND THE “P” STANDS FOR PROGRESSIVE SCANNING, INTERLACED SCANNING HAS A TENDENCY TO BLUR DURING ACTION SEQUENCES, THIS DOESN’T HAPPEN IN PROGRESSIVE SCANNING.
CCTV SYSTEMS • Cameras use impedance to synchronize signaling when connecting monitors and other inline equipment to the output of the camera. • Connecting two monitors to a single camera using a T-connector will not work properly.
CCTV SYSTEMS • Assume that both monitors are terminating monitors, they both only have 75 ohm input jacks. • If you simply connect them both to the same camera you will experience negative effects, such as signal fading, alternating contrast and even lost video framing.
CCTV SYSTEMS • Both present 75 ohms of impedance and thus signaling is affected, the correct way to connect two monitors to the same video source is to use a video loop through. • Most terminating monitors have a switch that toggles between 75 ohms and zero ohms. • This switch must be turned to the off position (zero ohms) at the first monitor and 75 ohms at the second.
CCTV SYSTEMS • The output of the camera is connected to the first monitor and then looped through to the second monitor. • The second monitor provides the proper 75 ohm termination. • Some monitors are auto-terminating, they sense whether a signal is being looped or not.