Video-Surveillance – CCTV
The safety of people and goods is a topic of concern increasing within the society. In order to safeguard what is most precious to them, restaurants, schools, factories and shops, among other activities and entities, are increasingly resorting to the various solutions available, intending to better control procedures, infrastructure and facilities.
With the flexibility afforded by its relationship with so-called new technologies, video-surveillance is one of security solutions for which demand has increased more in recent years.
However, on one hand the existence of cameras collecting images for a particular space, 24 hours a day, may appeal to because we feel safer, we should remember that this collection of images, and personal data, may interfere with the rights, freedoms and guarantees of the individual.
Some types of establishments may be required, under determined terms and conditions, to have a CCTV system of private security.
Video cameras can be an advantage with respect to control situations such as robberies or assaults and should be used for such purposes, but above all it’s very important that people know these systems and all the features they are assigned.
CCTV - what is it?
A CCTV system consists essentially of a set of cameras placed in strategic places, which capture and transmit images to a video management system that allows, among other things, viewing/recording of those images.
Using a video-surveillance system controlled from a control center allows the viewing of all movements of a large surface where there’s a large influx of people.
CCTV allows to view these images after its recording and, if any event is detected, to know their causes, which helps improve security with a preventive nature. Furthermore, the placement of visible cameras at strategic points contributes to deter any wrongdoing and give visitors a sense of security.
There are basically three types of CCTV systems:
- Analogue with Digital Recording
Analogue systems with Digital Recording
There was a time when the technology of CCTV systems was fully analogue and image recording was made on VHS cassettes.
In the early 90’s of the XXth century appeared the first systems of digital recording (DVR) and they offer many advantages far outweigh the benefits of the classic analogue recording systems, however, this generation of systems can not be considered pure IP, since it converts the analogue video signals to digital formats, which are then stored on a hard drive and can be accessed remotely over IP.
This technology has some advantages and disadvantages when compared to newer systems based on IP technology.
Advantages of systems based on Analogue cameras
Low cost - The analogue cameras generally have a lower cost than IP cameras.
Largest Variety – There are a lot more wide variety of models/types of cameras.
Compatibility - The ability of total integration of cameras from various manufacturers.
Disadvantages of systems based on Analogue cameras
Installation costs - The cable networks of these systems have higher costs and are limited to the maximum distance of transmission allowed by coaxial cable, because there is image degradation as a function of the travelled distance.
Expansion difficulty - The premises of systems based on analogue cameras are limited to the number of cameras allowed by the DVR, is sometimes necessary to replace the existing digital video recorder (DVR).
Lower resolution - The analogue image scanned rarely generates more than a definition of 0.4 Megapixel. IP cameras feature a 3 Megapixel resolution or more.
Types of analogue cameras
The cameras can be divided into three major groups:
- Normal Cameras They are the body cameras, the "bullet" cameras (cylindrical cameras), mini-cameras and "dome" cameras;
- Motion Cameras Usually referred to as PTZ cameras (Pan - horizontal scroll / Tilt - vertical displacement / Zoom - focal point variation) and PT cameras (Pan and Tilt), may be Speed Dome cameras (cameras whose movements can be performed at high speed - up to about 360°/s) and Low Speed Dome cameras (cameras whose movements are more slow - up to 120°/s);
- Hidden Cameras There are hidden cameras in PIR detectors, in smoke detectors and there are many other models of hidden cameras.
The first ones are the most used and are commercially available in various formats for many different applications.
The second ones are motorized cameras that allow direct the camera in different directions and remotely perform zoom and are usually used when you want to cover a large area with one camera and/or there is an operator for its operation.
The hidden cameras are used in very specific applications where you want to conceal their presence.
Cameras, understand the specifications:
Any specification sheet of a camera typically has the following set of specifications:
- Resolution (in TV lines)
- Sensitivity (in lux)
- Image Format (in inch)
- Voltage supply (in V - volts)
- Consumption (in A - amperes)
- SNR – Signal to Noise Ratio (in dB)
Of these specifications we can enhance the first two: Resolution and sensitivity.
The resolution of the cameras is usually measured in TVL (TV Lines) - is the smallest area of the object that the camera can distinguish.
The most common values for the resolution are: 330, 350, 380, 420, 480, 550 and 600 TVL.
This number of lines respect to the horizontal resolution. On specifications, usually doesn’t appear the number of horizontal lines because this number depends on the chip installed in the camera.
Sensitivity is usually measured in lux and indicates the minimum light level required to obtain a video image of good quality.
The lower the lux value specified for the camera, the better the image taken in low light conditions. For example, if we have a camera with 0.4 lux and another with 1.0 lux, the first can capture a good image in worse low light conditions.
Capture an image of good quality depends on where the cameras will be placed and what you want to view, depending on lighting conditions:
|Type of use||Recommended Cameras|
|During the day||~ 5.0 lux|
|Low-light indoor and outdoor with lighting by lamps||0.5 < lux < 2.0|
|Very low-light situations||Below 0.4 lux|
|Without any light||It’s recommended the use of infrared artificial lighting in conjunction with Black & White cameras. Alternatively, can be used Day & Night colour cameras commuting to Black & White in low light situations, also in conjunction with infrared illumination.|
Currently there are several image formats, which depend on the CCD camera, highlighting the shapes of 1/2”, 1/3” and 1/4”.
A lens designed for a specific image format can always be used in a device with a smaller image size, but never on a device with an image size larger.
Power consumption is measured in amperes (A).
The usual electrical consumption of cameras is around 120mA (power consumption of the camera without infrared illumination active).
The power consumption of a camera with the IR illumination active is around 600mA.
It’s possible to feed more than just a camera with a transformer since the sum of the currents of the cameras connected to this transformer does not exceed the current value that can be supplied by it:
Always check the voltage applied to the cameras
When power is 12Vdc, the distance between the power supply and the camera is very important because the tension decreases with the length of the cable due to its specific resistivity.
With AC power the issue of distance is not a critical point.
SNR – Signal to Noise Ratio
The signal to noise ratio is an expression that allows us to quantify the signal quality of the camera, especially with low light levels.
The noise can not be avoided, just can be minimized.
The amount of noise depends on the quality of the CCD chip, of the remainder of the electronics of the camera, of external electromagnetic influences and also of the temperature at which the electronics is placed.
In practice, a CCTV camera with a ratio SNR greater than or equal to 48dB can be a good camera.
The higher the SNR better the camera
The HDTVI solution can enable customer to setup a complete new 720P/1080P resolution analog surveillance system with advantages of long distance transmission (500 meters) through coaxial cable. This new technology enables user to upgrade their existing standard resolution analog system with HD-TVI compliant cameras and DVRs.
Compared with other video surveillance technology, the new HDTVI(High Definition Transport Video Interface) solution can all all analog CCTV users to enjoy the HD resolution white without investing huge amount of money in rewiring the existing coax cable infrastructure. The top-notch HDTVI camera can deliver latency-free 720P/1080P high definition video over up to 500 meters. Just replacing your cameras and DVRs with HDTVI compatible products, you can seamlessly upgrade your system to a HD analog system. As one of video surveillance manufacturer, Unifore is proud to present its latest 720P/1080P cameras which come with different types such as standard box, bullet, vandal-proof dome, PTZ camera.
Like traditional CCTV systems (analogue), this kind of video surveillance system allows to achieve the objectives of security and management required.
It’s distinguished by the fact that the transmission of sound and image be made via the intranet at the premises of the organization, which in some cases may be an added value and convenience for the end user.
IP cameras, as they are linked directly to an IP network, enable users to view live images and audio from one location or multiple locations through the local network (LAN), Internet or intranet.
An analogue camera has a resolution of approximately 300,000 pixels, or 0,3 Megapixel; an IP camera may have resolutions of 3 megapixels or more. With resolutions of this size there is a great ability to identify and check the details in an image and are possible new features such as motion detection in the field of the viewing area and zoom simultaneously in various parts of the image, etc.
With analogue cameras images are carried via coaxial cable without any encryption or authentication, which allows anyone to view images from the camera. In contrast, IP cameras can encrypt files that are sent over the network, thus ensuring that only authorized persons view the images.
The image quality of an IP camera that records the image digitally native is far superior to analogue image scanned. This is not always noticed in viewing "live", however, this quality factor is clear when the recovery of the recorded image.
The images captured by such cameras are carried on the IP network through hubs, switches and routers and stored on a PC with the Management and Video Control (NVR) software.
It’s also a full video system based on network, where no intermediate analogue component is used; an IP video system uses the processing of IP cameras as a way to reduce bandwidth utilization.
A major advantage of this solution is the use of the infrastructure of existing structured network, as well as the possibility of supply via PoE (Power over Ethernet), or power through the cable network, which supports data transmission and feeding; the use of Wireless (WiFi) network devices; the possibility of integrated Pan/Tilt/Zoom, audio, digital inputs and outputs, devices actuation and greater flexibility and integration capability with other systems.
The expansion capacity of these systems is unlimited.
Fundamentals of IP Networks
- The IP address is a unique number that identifies your computer on a network.
- Each message contains information of which is the sending address and which is the destination address.
- In certain contexts, such as the Internet, are generically called gateways.
- Allow divide the network into segments watertight, in which packets of information to pass from one network segment to another, must necessarily pass through the router.
- There are routers for LAN (Local Area Network) and WAN (Wide Area Network).
- Define the rule for data transmission.
- It’s the entry point from one network to another - the gateway is responsible for proper distribution of data into and out of a local network. It’s usually a router or a computer.
- It’s a filtering module located on a gateway machine that examines all incoming and outgoing traffic to determine if it can be routed to their destination.
- The router provides a comprehensive firewall through its NAT functionality - the assignment of rules for specific IP addresses and the ability to record information of packets sent to a particular direction so that they may be allowed on the way back.
NAT (Network Address Translator)
- With NAT you can connect multiple computers on a network to another network through a single IP address, avoiding possible conflicts of identifying the IP addresses of computers on each network.
- It’s possible to connect an entire network using a single IP address, since the NAT module rewrites the source address in packets sent from computers on your local network with the address of the router.
DNS (Domain Name Service/System)
- Usually we use a domain name because it's easier to remind oneself of a name than a sequence of numbers, the DNS resolves the problem of names from the viewpoint of the IP - for example, www.tecnicontrol.pt is a domain name that has an associated IP address, DNS matches the domain name to the IP address associated with it.
DHCP (Dynamic Host Configuration Protocol)
- It’s a protocol for organizing and simplifying the administration of IP addresses to local machines. In many cases, for simplicity, the DHCP server has an embedded DNS server. By specifying the IP address of a particular network device, DHCP uses the DNS values associated with that device.
LAN (Local Area Network)
- A LAN is a group of computers connected together with the possibility of sharing resources.
- The netmask is used to cluster IP addresses; there are a group of addresses assigned to each segment of the network. For example, the mask 255.255.255.0 groups a set of 254 IP addresses.
- If we have, for example, a subnet 18.104.22.168, masked as 255.255.255.0 the addresses we can assign to computers on the subnet will be from 22.214.171.124 to 126.96.36.199.
- Port numbers are 16 bits (1 to 65535) used by TCP and UDP and are used to address applications (services) that run on a computer.
- If there was only a single network application running on your computer would need no doors because the IP address was sufficient to address the service.
- The port number can be seen as the address of an application within the computer.
Some common ports are:
- File Transfer Protocol (FTP) Port 21
- Telnet Port 23
- Simple Mail Transfer Protocol (SMTP) Port 25
- WWW server (HTTP) Port 80
- Domain Name Server (DNS) Port 53
- Allows connection of computers in a star network which facilitates the installation and system maintenance.
- Most Switches has a number of LED that let you control the flow of global information and/or door by door.
It’s important to consider the compression method used by an IP camera, the compression reduces the size of the video files generated during image capture. The video files contain a huge amount of data so that is required the data compression to reduce storage requirements and bandwidth.
The most widely used compression techniques are MPEG-4 and MJPEG.
M-JPEG (Motion JPEG)
Motion JPEG or M-JPEG is a sequence of digital video that consists of a series of individual JPEG images (JPEG - Joint Photographic Experts Group) which, when displayed at 16 frames per second or more, allow them to be perceived as moving video. The video in full motion is perceived at 30 frames per second in NTSC and 25 frames per second in PAL.
The IP cameras using this type of compression can capture images at a maximum rate of 30 frames per second.
In this type of compression the bandwidth needed for transmission and disk space required for storage are very high.
With MPEG4, only a small fraction of the total image is sent as a complete image.
In image capture from a camera most of images are similar, differing only when motion occurs; in this format is sent only the data corresponding to the differences from the previous images.
The result is reduced bandwidth usage and storage space, however, MPEG4 has a lower image quality when compared with the M-JPEG.
H.264 or MPEG-4 Part 10/AVC
H.264, also known as MPEG-4 Part 10/AVC (Advanced Video Coding), is the latest MPEG standard for video encoding, hoping that this becomes the preferred video standard in coming years.
An H.264 encoder can, without compromising image quality, reduce the size of a digital video file by more than 80% compared with Motion JPEG, and 50% more than the standard MPEG-4.
This means it will need much less network bandwidth and storage space for a video file, in other words, you can get a video quality much higher for the same transmission speed.
An IP camera has an embedded web server which enables the transmission of live images through an IP network such as a LAN, Intranet or Internet.
Standard IP Cameras and Megapixel IP cameras
There is a big difference between the standard IP cameras and megapixel IP camera:
The standard IP cameras generally have the same resolution as an analogue camera with the addition of having a video encoder to convert the analogue signal to an IP address.
Megapixel IP cameras are high definition cameras that provide high-resolution images (1.3, 2, 3, 5, 8 or more megapixels), this type of camera provides images in which the resolution contains 30-50 times more detail than an analogue camera, allowing cover larger areas without loss of resolution, see better those details and identify people and objects with higher image resolution - a key element in video surveillance.
Advantages of IP cameras:
- Do not need a computer for images to be sent to Internet or IP network.
- No need for software or additional cards for normal operation.
- They are easy to install and have their own IP address, which automatically connects it to the network via a hub/router.
- Allow viewing MPEG-4 recording and simultaneous Motion JPEG.
- Provide, in many of them, a two-way audio communication.
- Images and audio can be encrypted ensuring the integrity and privacy.
- Allow access to video and audio through a web browser and an Internet connection.
- The image quality of an IP camera is far superior to digitalized analogue image.
- They can use the existing structured cabling network, facilitating their installation and reducing the cost of installation.
The lenses can be divided into four major groups:
- Large aperture lens (wide angle) – can cover a wide area but it is difficult to identify a person;
- Standard lenses – allow the same visibility that the human eye;
- Telephoto lens – have closed angle of view, but allows better distinguish objects.
- Can be used when it is not possible to obtain a lens with a focal length needed for a particular application or when you want more flexibility in order to select the best angle of vision.
- Have a variable focal length and are available in manual or motorized versions.
- Are very small lenses, largely used in hidden cameras.
Lenses, understand the specifications
Any datasheet of a lens has the following specifications:
- F-number or F-stop (most common)
- Depth of field
- Focal length versus angle or field of vision
- Iris control
- Type of mechanical docking C or CS-MOUNT
F-number or F-Stop
It’s the ability of a lens to "capture" light; it depends upon the relationship between the lens aperture and the focal length.
This relationship is represented by the letter "F", which is usually referred to as "F-stop."
A low number for the F-stop means a large aperture lens that delivers a good quality image in low light.
Example: A lens with an F-stop of 1.2 captures more light than a lens with an F-stop of 4.0, which gives a better picture in low light.
Depth of field
Depth of field is the distance before and after the object in the image that is still considered acceptably in focus, that is, when you want to focus accurately an object that is at a certain distance, the lens also focuses on the field a bit front and behind the object.
This image example of how the F-stop affects the depth of field
Depth of field increases or decreases according to the opening:
Lens focal length
- Lens angle (ex. 2.8 mm) → greater depth of field
- Telephoto lenses (ex. 16mm) → smaller depth of field
- Large aperture (ex. f 1.2) → smaller depth of field
- Small aperture (ex. f 4.0) → greater depth of field
Distance to object
- Short distance (ex. at 5m) → smaller depth of field
- Great distance (ex. at 25m)→ greater depth of field
Focal Length vs. Field of View
The focal length is the distance in millimetres between the point of convergence of the light to the point where the focused image will be projected.
Field of view is the extent of the image that can be viewed by a particular lens due to its focal length. The greater is the distance the smaller will be the field of view and greater will be its power to approach the subject in focus.
The angle or field of view of a lens depends on two factors: the focal length and dimensions of the CCD.
- The "greater" is the CCD; wider is the viewing angle for a constant focal length.
- The "greater" is the focal length; lower is the viewing angle for a given CCD.
For the focal length, lenses can be classified into the following types:
- Monofocal lenses are lenses with a fixed focal length and each length corresponds to an angle of view (large, medium, narrow/closed). For example, lenses of 2.8, 4, 6, 8, 12, 16 mm...
- Lens with variable focal length (varifocal lenses), are lenses with variable focal length that is adjusted manually. For example, lenses 2:8-10, 3.5-8, 5-50 mm...
A wide angle lens has a short focal length and a telephoto lens has a large focal length.
Monofocal lens of 4, 8 and 12mm
Iris or lens diaphragm and its control
There are three types of Iris:
- Fixed Iris – It isn’t possible to make any adjustment.
- Manual Iris – In this type of iris its setting is done manually.
- Auto-Iris – Has an electric motor coupled to the lens to open and close the iris in order to adjust the amount of light incident on the CCD to increase the brightness latitude of the camera operation. Has two modes: DC drive (most common) and Video Drive.
The common cameras don’t use incorporated lens, which are interchangeable and can be used the same camera with several different lenses.
The lenses may or may not have a diaphragm like the cameras.
The lenses without iris are called “Fixed Lenses”.
Lenses with iris can have their control in a manual or motorized way.
The manual iris is manually tuned and can create blur with change in brightness.
Auto-iris is controlled by an electric motor which, coupled with a sensor that continuously measures the light levels, self-regulates the lens in order to always obtain the best clarity.
Type the mechanical interlocking C or CS-MOUNT
It is the industry standard for mounting (fitting) lenses in camera bodies.
The CS mount has a screw with 1" diameter and 32 steps per inch.
The distance of the lens surface to the sensor surface is of 0.492" (12.5mm).
How to select a lens for a given application?
There are generally two issues that should arise when we want to select a particular lens. These questions are:
Should I use a lens with fixed, manual or auto iris?
- If we want to save, we use a fixed iris lens or manual iris. These two types are recommended in situations where the lighting conditions have a limited range of latitude. For example: offices, interior areas with constant illumination, etc.
- To situations where the lighting suffers changes of great latitude the only solution are lenses with auto-iris (except in situations where the mechanics of the lens is unable to react to variations in light).
What focal length is needed?
- Short length à Wide viewing angle
- If applying for an office or a warehouse where it is intended to cover the maximum possible area then the best choice is a lens for example 2.8mm or 4mm.
- If you observe a limited area such as an entry the right choice will be lenses of 8mm and 12mm.
- Should use varifocal lenses if wanted greater flexibility to select the best viewing angle.
Note: The focal length to use will always depend on the distance from the camera to the object.
Whereas if you want to choose a lens to cover the area shown in the figure, where:
F - focal length (mm)
To determine the needed focal length use the expression:
F = v x D/h or F = c x D/l in which: c – Width of the CCD chip v – Height of the CCD chip
Another question is as follows:
In any area covered by a camera there are sub-areas, or moving objects that may be critical, and this is crucial when it’s asked a detection or identification of something; thus:
- To make a detection, it suffices that the critical area to be observed is 5% of the total area of the image.
- To see the action, it’s necessary that the critical area to be observed is 10% of the total area of the image.
- To make the identification, it’s necessary that the critical area to be observed is 25% of the total area of the image.
Consider having a camera with a CCD 1/3" and that with it intend to cover the entrance gate of a factory. Consider that the critical area is located at the gate way where enter the vehicles wished to identify.
The distance from the camera to the gate is D = 30.48m = 30480mm
The width of the gate is l = 3.65m = 3650mm
Knowing beforehand that the CCD 1/3" corresponds to: c = 4.8mm and v = 3.6mm
And defining that the critical area for the identification of a vehicle is 1.7m x 1.5m
Focal length f = 4.8 x 30480 / 3650 = 40mm
Height of area to cover h = v x D / f = 3.6 x 30480 / 40 = 2743.2mm = 2.7432m
Zone area to cover l x h = 3.65 x 2.7432 = 10m2
Critical area = 1.7 x 1.5 = 2.55m2
% of the vehicle on the monitor = 2.55 / 10 x 100 = 25.5%
We therefore conclude that, if you use a lens with a focal length of 40mm, you can get an identification (registration plate) clear of vehicles that cross the entrance gate of the factory and an image area of the gate corresponding to an area of 10m2 (3.65m wide and 2.74m height).
The high-resolution cameras MEGAPIXEL require adequate and superior quality lenses.
The high resolution images require higher-quality lenses.
The Megapixel cameras and the high definition (HD) movement have completely changed the rules for selection of lenses and are challenging manufacturers to produce lenses with higher performances.
Megapixel lens is not just an enhancement to the camera, but an essential element that enhances the quality of the captured images and, as such, when selected properly, can help take full advantage of megapixel images; a wrong choice can cause that the camera has a quality equal to or even lower than an analogue camera.
Selection of a Megapixel lens
The selection of the lens is particularly important for facial recognition or identification of a registration plate of a vehicle, which are common applications for megapixel cameras, which requires a high resolution image of both the center and the edge of the image, which is only possible when choosing a suitable lens.
Like the standard lenses, there’s also always taking into account the focal length that, similarly, also will depend on the distance from the camera to the object of focus.
However, the most important specification and where there’s greater variation between each type of lens megapixel is the modulation transfer function (MTF), this function is the ability and accuracy of precision that a lens has when transfers the information being viewed for an entire image, for each pixel of the CCD sensor, and determines the sharpness of images.
To understand how the lens can affect the performance of imaging systems, it is necessary to understand the physics behind the diffraction, lens aperture, focal length and wavelength of light.
One point of reference more useful to describe the image quality (lens performance) is the modulation function (MTF).
At its most basic definition, the MTF is how to describe the sensitivity to the contrast of a lens system. Compared to the human eye this could be regarded as visual performance.
A perfect lens would reproduce a complete picture of an object without any degradation, but unfortunately a perfect lens doesn’t exists; image sharpness, contrast, lighting, broadcasting spectrum and distortion affect the ability of a lens in the reproduction of an image.
A suitable lens reproduces the image of an object to the extent that a detail of that object can no longer be reproduced.
In conclusion, the MTF is therefore a contrast ratio of an object for an image.
In the optical industry, the MTF is measured in one unit of spatial frequency named Line Pairs per mm: Lp/mm.
Lp/mm - Line pairs per mm
The number of line pairs per millimetre (Lp/mm) is a widely accepted quantitative measure for measuring the resolution of a lens and is the most important specification for the choice of a suitable lens.
Line pairs (Lp) are groups of alternating lines and the greater the value the greater the ability of the lens to capture small details in an image.
For an analogue camera the acceptable value of a lens is about 30 Lp/mm, for a megapixel camera the minimum value is 60 Lp/mm. Because of the higher resolution sensor megapixel, megapixel lenses need to capture more details.
The best way to determine the required Lp for a given camera is dividing the number of pixels on the chip width by number of pixels in height and then divide by two (pairs of lines).
The megapixel cameras equipped with lenses that provide high-resolution images in both the center and the edge of the image have a greater accuracy and precision of alignment with the CCD.
Usually the specifications provided by manufacturers as to the resolution of the lenses are based on the center of the image and refer to the number of pixels or dots that can be discerned in the center of the lens and not necessarily at the edges.
However, as many manufacturers still do not give the Lp/mm of the lenses, are recommended other methods of correspondence.
For example, many manufacturers assess the lenses for a given megapixel CCD size, (usually 1.3, 3, 5 etc.) or standard image format 1/2", 1/3” or 1/4" etc.).
The practical importance is that the Lp/mm is only relative to the size of the pixels in the camera, for example, a lens of 120 Lp/mm can be very good for a 1.3MP camera using a 1/2" sensor and insufficient to a 2MP camera using a 2/3" sensor.
Increasingly, CCTV is taking IP technology but most of the existing systems are still analogue.
The hybrids DVR facilitate easy integration of existing systems with the latest IP technology, enabling an implementation of CCTV/IP at lower costs.
These systems make use of both technologies, analogue and IP, reusing and integrating in the same system, the existing analogue cameras and cabling and new IP cameras and can still make use of an existing structured cabling network and thus significantly lower costs transition from an analogue system to an IP system, allowing its gradual evolution.
Power circuits of CCTV systems should be stabilized and centralized in a restricted location, for example in a technical area, which could prevent the interruption of operation by third parties.
Image transmission through coaxial cable
The conventional CCTV systems send the image as a composite video signal through a coaxial cable from each camera to the receiver equipment/DVR.
Image transmission through UTP cable
For analogue cameras
For installations where there are problems with passage of cables or very long distances, it’s possible transmit images via UTP cable, making it easy to install and maintaining the quality of the signal emitted by the cameras, being possible even the passage of several video, audio and data simultaneous signals on a single UTP cable.
For the use of UTP cable for transmission of these signals are used passive converters, which do not require external power, and active converters, which require external power and allow, in the case of video transmission, cover greater distances.
For IP cameras
The cabling systems for CCTV/IP use UTP cable and its installation follows the rules of the structured cabling networks to voice and data (see Copper and Optical Fibre Structured Cabling Networks)
Examples of connecting analogue CCTV systems with inclusion of video, audio and data converters over UTP cabling
Short distance basic applications
Passage of the video signal through UTP cable to a distance up to 600m (B&W) or 300m (colour)
Passage of the video signal and power to the converter and camera through UTP cable without using power cord to a distance up to 50 m
Passage of 4 cameras simultaneously on a single UTP cable Power and video signal is sent on a single UTP cable
Long distance basic applications
Image transmission of a colour camera at a distance of 1500m, using a passive emitter (powerless) and an active receiver (powered)
Long distance serial connection
Colour image transmission at a distance of 3000m using a serial link of passive emitters (powerless) and active receivers (powered)
Main advantages of image transmission over UTP cabling
- Easy installation
- Save time and wiring
- Alternative to the use of optical fibre at a fraction of the cost
- It’s suitable for application in large CCTV systems where it’s necessary to install many cameras or where it’s difficult to pass coaxial cable due to the size of existing pipes
Some examples where it will be very useful to use such solution are:
- Car Parks
- Shopping Malls
- The PABX