Monitors

Professional CCTV monitor - SAMSUNG SMT-1922P M3019 - is designed for continuous operation,
in both analog and digital video monitoring systems

A monitor is a device that changes electric signals to optical information suitable for the human eye. Monitors have to fulfill safety standards, which means that they must have CE certificates.

Monitors should work properly up to 90% humidity, and in temperature range from 0^oC to +40^oC. Some manufacturers specify the temperature range from -10^oC to 55^o C.

Adjustments.

Besides the power on/off switch, every monitor usually has the following adjustments: H-hold, V-hold, contrast, brightness, color saturation (color monitors), sharpness.

Color LCD monitors.

These monitors have become the standard in modern CCTV installations. Their biggest advantage is small depth, they need little space on the operator's desk, or can even be mounted on a wall in the monitoring center. The popularity of LCD panels in CCTV applications is the result of large scale manufacturing and low price - they are mainly used as computer monitors. However, the typical PC monitors can only be used with devices equipped with VGA output.

The group of LCD monitors dedicated for CCTV applications are professional devices with CVBS inputs, e.g. MTC-19A1-3D+VGA M3119. The monitor has standard BNC inputs for connecting any CCTV video devices using PAL standard, like DVR, CCTV camera, video splitter etc.

Another group of displays that are often used in CCTV systems are universal PC/TV LCD implementations, usually available at very competitive price. Aside from built-in TV tuner, the panels have been equipped with video inputs suitable for connecting CCTV devices. LCD televisions are also used when one needs bigger screens, over 22".

When using analog CCTV cameras, the LCD monitors should have 4:3 aspect ratio. Most of such cameras provide images in this format and they would be deformed on displays with 16:9 aspect ratio. The latter are used in IP-CCTV systems. The role of a DVR is performed by dedicated PC and special software that can adjust the images from the cameras to screen parameters of the monitor used.

Small thickness of LCD monitors allows to use them in places where CRT solutions were practically not possible. LCD monitors in metal vandal-proof casings are mounted in vehicles. Larger panels, up to 21", mounted e.g. in buses (public transport) work as information/advertising/entertainment screens. The smaller ones, mounted close to the driver, allow him/her to monitor the inside of the bus.

The main parameters of LCD monitors include maximum contrast and brightness, pixel response time, horizontal and vertical viewing angles. Additional differences concern the number of audio and video inputs/outputs, built-in speakers, the way of mounting.
Choosing an LCD monitor it is important to know the terms of warranty concerning possible degradation of the screen (falling-out pixels). This phenomenon is not so irritating as in the case of a PC monitor, but also lowers the quality of images.

LCD monitor in London's bus.

Use of PC monitors with external VIDEO/VGA converters.

These converters change standard video signal (CVBS) to VGA standard. They allow to connect a CCTV camera, satellite receiver, DVD player, video cassette recorder or other video signal source to a standard VGA monitor.

Audio paths in CCTV monitors.

Many monitors are equipped with built-in audio amplifiers and speakers. It allows to listen in at cameras' locations thanks to microphones either built in the cameras or placed in their brackets (subject to the local law). They usually use RCA connectors or 3.5 mm mini-jacks. Audio modules require input signal levels within the range of 10-150 mV_p-p. Additional volume adjustments can be found on the front panels of the monitors. This function is related to the fact that most of the offered DVRs have audio recording feature. In the case of audio playback, the user will not have to worry about purchasing and installing additional amplifier and loudspeaker/s.

Choosing a CCTV monitor.

There are monitors with diagonal from 4 to 42 inches. A typical diagonal, recommended for operation with a DVR, is 19". Smaller monitors are used when there is not enough space or as secondary ones, usually for full screen viewing. When selecting the size of a monitor, one should take into consideration the comfort and ergonomics of the final user (guard) who watches the screen. The general rule is - the bigger the better - of course within reason.

Size of objects on a monitor's screen. According to EN 50132-7 norm, the size of the representation of an object, e.g. human figure should be strictly connected with the aim of the operator - identification, recognition, detection or general observation. For CCTV systems having resolution better than 400 TVL, the representations of human figures should be as follows:

• for identification purposes - the figure should cover at least 120% of the screen's height;
• for recognition purposes - the figure should cover at least 50% of the screen's height;
• for intrusion detection purposes - the figure should cover at least 10% of the screen's height;
• for crowd control - the figures should cover at least 5% of screen height.

Number of monitors and their sizes. The number of monitors should be based on:

• number of installed cameras;
• functional features;
• number of operators working at the same time.

Number of cameras to number of monitors ratio shouldn't usually be higher than 10:1.
The number of monitors should allow to display all simultaneous alarms (given in user specification requirements).

The size of a screen should also be adequate to the distance from which the screen is watched.

The recommended distance between eyes and a screen is approximately 3 - 5 times larger than its diagonal (it also depends on the resolution of the image).

The implemented DNIe(TM) function (Digital Natural Image engine) improves image quality through advanced algorithms - of noise reduction, detail emphasizing, contrast and brightness optimization.