What books can I read if I want to learn security monitoring?

Summary of basic knowledge of safety monitoring (suitable for beginners)

First, lens analysis

1. lens type (classified by application)

Wide-angle lens: the viewing angle is above 90 degrees, the nearby image is distorted, and the observation range is large.

Standard lens: the viewing angle is about 30 degrees, and it has a wide range of use.

Telephoto lens: The viewing angle is less than 20 degrees, and the focal length can reach tens or hundreds of millimeters.

Zoom lens: the focal length of the lens is continuously variable, and the focal length can be changed from wide angle to telephoto. The longer the focal length, the larger the imaging.

Pinhole lens: used for hidden observation, often installed on the ceiling or wall.

2. The relationship between the size, distance and focal length of an object.

Suppose the width and height of the object are w.h, the distance between the object and the lens is L, and the focal length of the lens is F. ..

3. Relative aperture

In order to control the luminous flux passing through the lens, an aperture is set behind the lens. Assuming that the effective aperture of the aperture is D, the actual effective aperture of mirror light is D, which is greater than D. The ratio of D to focal length F is defined as the relative aperture A, that is, A = D/F. The relative aperture of the lens determines the illumination of shooting, and the reciprocal of the illumination of the image and the relative aperture of the lens represents the size of the lens aperture. The smaller the f value, the larger the aperture and the greater the luminous flux reaching the ccd chip. Therefore, in the case of the same focal length f, the smaller the value of f, the better the lens.

4. The focal length of the lens

1) fixed focal length: the focal length is fixed and can be divided into two types: aperture and non-aperture.

Aperture: The aperture of the lens can be adjusted. According to the change of environment, the aperture should be adjusted accordingly. The aperture can be adjusted manually or automatically. If you adjust the aperture manually, it is called manual aperture. If the lens comes with a micro-motor to automatically adjust the aperture, it is called automatic aperture.

No aperture: that is, fixed aperture, and its luminous flux is fixed. It is mainly used when the light source is constant or the camera has its own electronic shutter.

2) Zoom: The focal length can be adjusted as required to enlarge or reduce the image of the subject. Commonly used zoom lenses include six-fold zoom and ten-fold zoom.

Trivariate and bivariate lenses

Three variable lenses: adjustable focal length, adjustable focal length and adjustable aperture.

Variable lens: adjustable focal length, adjustable focal length, automatic aperture.

5. The principle of matching lenses first

In order to obtain the expected camera effect, we should pay attention to six basic elements when choosing a lens:

A) the size of the object

B) Detailed size of the object to be photographed

C) object distance

D) focal length

E) the size of the target surface of e)ccd camera.

F) Resolution of lens and camera system

Operating steps:

* Remove the lens anti-tilt device and connect the lens.

* If using cs lens, please lower the C-ring (5mm) and lock the cs lens device.

* c lens can be directly installed and used.

* Connect the video output (bnc) to a monitor or other device.

* plug in dc 12v power supply /ac220v * and check whether the led is on.

* When the image is blurred, please adjust the focal length of the lens.

Second, the monitoring system equipment introduction

① Yuntai

In the previous introduction, we often mentioned Yuntai, but some people don't have any perceptual knowledge about it. Yuntai is actually an installation platform composed of two alternating currents, which can move horizontally or vertically. The pan-tilt we are talking about is different from the pan-tilt in photographic equipment. Generally speaking, the tripod head of photographic equipment is just a tripod, and the orientation can only be adjusted by hand. The pan-tilt mentioned in the monitoring system can control its rotation direction at the far end through the control system. Yuntai is divided into indoor type and outdoor type according to the use environment. The main difference is that the outdoor type has good sealing performance, waterproof and dustproof, and heavy load. According to the installation method, it can be divided into side installation and hoisting, that is, whether the tripod head is installed on the ceiling or on the wall. According to the shape, it can be divided into ordinary type and spherical type. The spherical tripod head is placed in a hemispherical and spherical protective cover, which is hidden, beautiful and fast except for preventing dust from interfering with images. When selecting the pan/tilt, we should consider the installation environment, installation mode, working voltage and load size, as well as the cost performance and beautiful appearance.

② Support

If the camera only monitors a certain position and does not need to rotate, then only the camera bracket can meet the requirements. Ordinary camera brackets are simple to install, low in price and various. There are four kinds of common supports: short, long, straight and curved, and different models are selected according to different requirements. Outdoor supports mainly consider whether the load-bearing capacity meets the requirements, and then the installation location, because in practice, we find that many outdoor cameras are installed in special locations, some are installed on telephone poles, some are installed on tower cranes, and some are installed on iron frames ... For various reasons, the existing supports may be difficult to meet the requirements and need to be processed or improved, so I won't say much here.

③ Protective cover

Screen door is also one of the most commonly used devices in monitoring system, which is mainly divided into indoor and outdoor. The main differences between indoor protective covers are size, beautiful appearance and qualified surface treatment. The function is mainly to prevent dust and damage. The sealing performance of the outdoor protective cover must be good to ensure that rainwater cannot enter the protective cover and corrode the camera. Some outdoor protective covers also have exhaust fans, heating plates and wipers, which can better protect the equipment. When the weather is too hot, the exhaust fan automatically works; When it is too cold, the heating plate automatically works; When there is rain on the protective cover glass, the wiper can be started through the control system. When choosing a protective sleeve, look at the overall structure first. The fewer mounting holes, the better the water resistance. Then see if the internal wiring is easy to connect. Finally, consider the appearance, weight, mounting seat and so on.

④ Monitor

Monitor is the standard output of monitoring system. With the monitor, we can watch the images sent by the front end. The monitors are available in color and black and white, with sizes of 9, 10, 12, 14, 15, 17, 2 1 inch, etc. , commonly used is 14 inch. The display also has resolution, which is expressed by the number of lines like the camera. In practical use, it is generally required that the number of lines of the display should match that of the camera. In addition, some monitors also have audio input, s-video input, rgb component input and so on. Except for the audio input monitoring system, most other functions are used for image processing, so I won't introduce them here.

⑤ Video amplifier

When the video transmission distance is long, it is best to use a video line with large line diameter, and at the same time, a video amplifier can be added to the line to enhance the signal strength and achieve the purpose of long-distance transmission. Video amplifier can enhance the brightness, chroma and synchronization signal of video, but the interference signal in the line will also be amplified. In addition, too many video amplifiers cannot be connected in series in the loop, otherwise saturation will occur, resulting in image distortion.

⑥ Video distributor

A video signal corresponds to a monitor or a video recorder. If you want to send a camera image to multiple managers, you'd better choose a video distributor. Due to the large attenuation of the parallel video signal, the image will be seriously distorted and the line will be unstable after being sent to the multi-channel output equipment due to impedance mismatch and other reasons. In addition to impedance matching, the video distributor also has video gain, so that video signals can be sent to multiple output devices at the same time without being affected.

⑦ Video switcher

Multiple video signals should be sent to the same place for monitoring. One video can correspond to one monitor, but the monitor occupies a large area and is expensive. If it is not necessary to monitor all the time, a switch can be added in the monitoring room to connect the output signal of the camera to the input end of the switch, and the output end of the switch is connected to the monitor. The input end of the switch is divided into 2, 4, 6, 8, 12, 16 channels, and the output end. The switch has two working modes: manual switching and automatic switching. Manual mode is to set the switch in any way you want. Automatic mode is to switch preset videos in turn with delay, and the switching time can be adjusted by a knob, generally between 1 sec and 35 sec. The switch is cheap (usually only three or five hundred yuan), simple to connect and easy to operate, but only one image can be seen at a time. To watch multiple camera images on one monitor at the same time, you need to use a picture splitter.

⑧ picture divider

There are four-minute, nine-minute and sixteen-minute picture splitters, which can simultaneously display the images of 4, 9 and 16 cameras on one monitor, or send them to a video recorder for recording. Four-segment is one of the most commonly used devices, and its cost performance is good. The quality and continuous performance of images meet most requirements. Nine segments and sixteen segments are expensive, and the resolution and continuity of each image will decrease after segmentation, and the video recording effect is not good. In addition, there are six-point, eight-point and double-quarter devices, but the image proportion, clarity and continuity are not ideal, and the market utilization rate is even smaller. Most splitters can not only display images at the same time, but also display a single picture, which can superimpose time and text, set automatic switching and connect alarm equipment.

Pet-name ruby video recorder

The most commonly used recording devices in the monitoring system are civil video recorders and long delay video recorders. Because of its simple operation and easy learning, video tapes are also easy to save and buy. Different from home video recorders, time-delay video recorders can work for a long time, record images for 24 hours (using ordinary vhs video tapes) or even hundreds of hours, connect alarm devices, automatically start recording when receiving alarm signals, superimpose time and date, make automatic recording programs for video recorders, select recording speed, and whether to automatically stop or rewind at the end of recording ... Although time-delay video recorders have outstanding performance, they are expensive, and the current resolution is not very high, so time-delay video will lose images.

Third, the choice of digital hard disk video recorder

At present, it can be said that it has entered the Spring and Autumn Period and Warring States Period of digital monitoring host. Objectively speaking, digital products are outstanding in hard disk video recording, network interaction, video alarm, work schedule, multi-screen display, etc., and have won the favor of many people, and gradually occupy a place in many fields such as security monitoring, teller monitoring, and civil monitoring. Because this field is developing rapidly, there is no national or industry standard. This paper introduces some matters needing attention and skills in selecting and evaluating digital products, hoping to help you choose a digital monitoring host.

1. View the selection of the interface

Most digital monitoring hosts choose industrial control cabinet as the shell, and the appearance should be exquisite and beautiful. It is helpful to lock the floppy drive and power switch with a mechanical lock. If you can open the lid, pay attention to what fan and power supply are used. For example, the average trouble-free working time of special fans on Pentium III III ⅲcpu is more than 3 years, while the average trouble-free working time of general fans may be inaccurate, which is a hidden danger for digital monitoring hosts that are constantly powered on every day. In addition, pay attention to the convenience of interface wiring in the back row.

For the convenience of operation, the interface should be in Chinese, and the main functions can be clearly reflected in the main interface. It is recommended to choose a professional and beautiful interface with intuitive operation. It's better to be menu-based like windows operation.

The function has strong expansibility, and the main functions are divided into monitoring function, video recording function, alarm function, control function, network function, identity recognition function and work schedule function. If there is a matrix, duplex intercom is the best, which is difficult to do. The following are introductions.

2. Diversification of functions

(1), monitoring function

Monitoring function is one of the most important functions of matrix host and digital host. The monitoring function is nothing more than seeing the whole scene clearly. Make a sound when necessary, and pay attention to whether the video and audio are synchronized. The effect of monitoring is mainly determined by the clarity, the real-time degree of the picture and the display form. Different from TV display, different graphics cards and acquisition cards have different observation effects. Just like measuring the definition of ccd camera, it is suggested to choose professional graphics test cards and cameras with high line numbers as the observation objects, and accurately read out the observable horizontal and vertical resolutions as the basis for monitoring the definition. Generally, when the image exceeds 17 frames per second, the naked eye looks like a real-time image, while the teller system and some special monitoring places require the image to reach more than 25 frames per second. Usually you can do some quick hand movements to observe this function, such as counting quickly and clapping your hands. The display forms are generally 1, 4, 7, 9, 10, 16, etc. And the screen can also be cut to full screen. The brightness, contrast, color, saturation and other parameters of each channel should be continuously adjustable, otherwise the multi-screen will not look well because of uneven light, which is also the place where the digital host is superior to the ordinary screen splitter. Full-screen observation can accurately reflect the image quality, video recording speed and graphics card quality.

(2) Video:

Video recording effect is the core and vitality of digital host. It is not necessarily good to see real-time and clear images on the monitor, but the most important effect of obtaining evidence depends on the video recording effect. Generally speaking, the video recording effect is more important than the monitoring effect.

The observation method of clarity and real-time degree is similar to the monitoring effect. The memory used for video recording per unit time and the memory of a single picture are also the most important parameters to reflect the video recording effect. The memory occupied by video recording per unit time and the space occupied by a single format have a decisive influence on the rate at which Takuwa images can be recorded on the same hard disk and transmitted on the Internet. Generally, the standard mpeg format records 600m per channel per hour, and the mjpeg format records 16 channels at the same time, accounting for 150m in standard cases. The space difference is quite big. How much memory a still picture takes up depends on the picture size, image compression ratio (image quality) and graphics format. How much memory a dynamic picture takes up depends on its size, compression ratio, format and whether it changes. I once tested a digital host, using mjpeg format, and the image size was set to 800×600. When moving, the image occupied 3k bytes, and when not moving, it was 180 bytes. In addition, some security monitoring hosts should have preset alarm video recording function, which can filter out information unrelated to alarm and greatly reduce the requirements for storage capacity. Some hosts also have the function of automatically increasing the number of recorded frames after alarming. This is also very helpful for the storage of effective information.

It should be noted that the quality of the same image is similar, but the occupied space may be very different (70m-550m/ road/hour). At this time, you can't see the display of the monitoring interface of the machine, so you can only retreat to the operating system (such as windows, nt, UNIX…… ...) to check the file size accurately.

(3) Alarm function:

The alarm function mainly refers to the input alarm of the detector and the alarm of image and video frame measurement. After the alarm, the system will automatically turn on the video recording function, and turn on the corresponding spotlights, alarm signals and networking output signals through the alarm output function.

Image and video frame detection and alarm is a unique function of digital monitoring, which can easily set the video trigger area and sensitivity, and can play the role of detector in a certain sense.

Automatic arming and disarming according to time period, preset alarm video and automatic framing of alarm video are all functions that traditional alarm systems do not have.

The output time of alarm signal should be adjustable, and all kinds of alarm results should be clearly recorded in the computer.

(4), control function:

It mainly refers to the control of the pan/tilt and lens of the omni-directional camera through the host computer, usually through a special decoder, mainly to observe whether the operation is flexible.

(5), network function:

Dial-up Internet through local area network, and various monitoring and video control operations can be carried out on the host through simple identification.

4. Introduction of ultra-low illumination camera and infrared lamp

With the development of semiconductor technology in recent years, ultra-low illumination camera is a popular product in monitoring industry. At present, it has been widely used in finance, culture, hotels, office buildings, residential property management and other fields. Because the traditional camera can't meet the demand of 24-hour continuous monitoring (because it is impossible to turn on the light anywhere for 24 hours), the ultra-low illumination camera based on new technology seized this opportunity and developed rapidly.

General ultra-low illumination cameras mostly use exview had technology, and the sensitivity of cameras using exview had ccd to external light will be greatly improved, and the sensitivity in the near infrared region can be improved to four times that of ordinary cameras, as shown in figure 1. Therefore, even in a very dark environment, this kind of camera can usually see objects that people can't see. The emergence of this technology has been welcomed by the monitoring market, and it can show the best effect in all kinds of lighting environments, especially with special infrared lighting equipment, which can obtain high-definition black and white images and realize the monitoring of 0 illumination (without lighting at all). In the near infrared region of 760mm- 1 100mm, a clear black-and-white image can be obtained if infrared illumination with appropriate wavelength is used.

Similarly, the method of acquiring images in low illumination is to increase the exposure of ccd in a single frame image by accumulating charges in a single frame, thus improving the sensitivity of the camera to a single frame image. This method can also get a lower illumination index, but it needs to reduce the consistency of the image. Therefore, when choosing this camera, we should pay attention not to cooperate with the pan/tilt as much as possible, otherwise it will cause the phenomenon of picture loss. There are some other methods to obtain images in low illumination, but none of them can fundamentally solve the illumination problem.

In addition, we should pay attention to several points when choosing to use low-light camera and infrared lamp.

First of all, choose the right lens. In order to improve the sensitivity of the camera to infrared light and scenery, we should choose a lens with a large amount of light as much as possible, and pay attention to opening the driving stage of the aperture as much as possible when using automatic aperture or electric variable lens. Because generally, with the increase of lens focal length, the luminous flux will decrease relatively, so we should leave a certain margin when choosing infrared lamps, and pay attention to the nominal index of infrared lamps.

Secondly, the matching power supply of infrared lamp should try to meet the minimum electric power required, and the irradiation distance is often not enough.

Third, we should consider the degree of reflection of the shooting scene. Because infrared ray has the same reflection and refraction characteristics as visible light, if there is no good reflection environment around the target scene (such as buildings, fences, signs, etc.), a certain distance margin should be considered.

Verb (abbreviation of verb) Yuntai

Pan-tilt is the supporting equipment for installing fixed cameras, which can be divided into fixed and electric pan-tilt.

Fixed pan/tilt is suitable for occasions with small monitoring range. After the camera is installed on the fixed pan/tilt, the horizontal and pitching angles of the camera can be adjusted, and the adjustment mechanism can only be locked after reaching the best working posture.

The electric pan-tilt is suitable for large-area scanning and monitoring, which can expand the monitoring range of the camera. The high-speed attitude of the electric pan-tilt is realized by two executive motors, which receive the signals from the controller for accurate operation and positioning. Under the action of the control signal, the camera on the tripod head can not only automatically scan the monitoring area, but also track the monitored object under the control of the personnel on duty in the monitoring center.

According to the rotation characteristics of the tripod head, the tripod head can be divided into a horizontal tripod head that can only rotate left and right and an omnidirectional tripod head that can rotate left and right and up and down. Generally speaking, the horizontal rotation angle is 0 ~ 350 and the vertical rotation angle is+90. The horizontal rotation speed of constant-speed pan-tilt is generally 3 ~ 10/s and the vertical speed is about 4 /s s. The horizontal rotation speed of variable-speed pan-tilt is generally 0 ~ 32/s and the vertical rotation speed is about 0 ~16/s. In some high-speed camera systems, the horizontal rotation speed of pan-tilt is above 480/s and vertical.

Six, hard disk video recorder product features:

The basic function of hard disk video recorder is to convert analog audio and video signals into mpeg digital signals and store them on hard disk (hdd), providing functions corresponding to recording, playing and managing programs.

Its outstanding features are reflected in the following aspects.

1. The digital high fidelity storage of analog programs is realized. Analog audio and video programs widely disseminated and collected by individuals can be recorded and stored in an advanced digital way. Once recorded and played repeatedly, the quality will not decrease.

2. Integrated input and output interface provides antenna/TV cable, av terminal, S terminal input interface and av terminal, S terminal output interface. It can record almost all TV programs and signals output by other players and cameras, and it is also convenient to connect other audio-visual equipment.

3. Multiple optional image recording levels provide three image quality recording levels for the same program source: high, medium and low. When the highest level is selected, the recorded image quality is close to dvd.

4. Large-capacity long-term program storage with strong expansibility. Users can choose 20.4gb, 40gb or more hard disks for program storage. Based on the capacity of 20.4gb, the relationship between recordable program times at the selected bit rate is shown in the following table:

Bit rate (mbps) Recordable program time (hours)

6 7

4 10

2 20

1. 15 38

5. It has advanced time shift function. When the TV program must be interrupted, the user only needs to press the timeshifting key, and the program from the interruption time will be automatically saved. After handling the transaction, the user can continue to watch the program from the interrupted position without any pause.

6. Perfect reservation recording/playing program function. Users can freely set the start time, length of time and other options to start recording/playing programs. By editing and combining the reserved programs, we can systematically record various intermittent TV programs, including TV dramas.

7. Powerful users of the network information home appliance center will be able to use a dvr-customized web browser through the network communication interface, and be equipped with corresponding network resources to enjoy rich online information.

8. Provide a convenient way to manage recorded programs. Users can sort and classify the recorded programs according to the recording time and program type, and set bookmarks at their favorite locations at will.

9. Provide free play mode Because of the fast and random storage characteristics of hard disk, you can enjoy recorded and recorded programs in a more flexible way than current dvd players, with smoother images when playing fast and higher detail resolution when playing slowly.

Seven, the selection skills of optical transceiver in security engineering.

At present, there are many kinds of technical indexes involved in multi-channel digital video optical terminals on the market. Most engineers and users lack corresponding means to judge the rationality and authenticity of technical indexes, and it is easy to get lost when choosing products. This paper describes two key technical indexes that are easy to verify in engineering, and emphatically analyzes how to choose multi-channel digital video optical transceiver in security monitoring engineering from the aspects of feasibility and practicability.

1. Review technical indicators

Multi-channel digital video transceiver can have multiple functions, and each function has corresponding technical requirements, such as video index, audio index, asynchronous data index, Ethernet index and so on. Specific technical indicators can require manufacturers to provide third-party testing certificates, and qualified engineers should conduct re-examination according to the indicators provided by manufacturers before purchasing equipment to test the actual technical indicators of equipment and the integrity of manufacturers. Here, the following two video indicators are briefly explained from the engineering point of view.

1. 1 3db video bandwidth is sufficient.

Video bandwidth is a cliche. When the video bandwidth is insufficient, the details of the monitoring picture are not clear enough, the horizontal resolution is low, and even serious color distortion or loss occurs. It is precisely because of the importance of video bandwidth to image quality that some unscrupulous manufacturers deliberately exaggerate the video bandwidth of their products to deceive customers. A manufacturer's multi-channel digital video transceiver claims that its video bandwidth is 8m, but its published video sampling frequency is12.5m. According to Nyquist sampling law, in order to truly restore the signal, its sampling frequency should be at least twice the signal frequency. In this case, the theoretical video bandwidth of this manufacturer's optical transceiver can't exceed 6.25m in any case. Obviously, this is a lie that exaggerates performance and deceives customers. Manufacturers without commercial reputation should not consider buying it. But not all customers can accurately identify the lies of manufacturers. For ordinary engineers and users, the video bandwidth of equipment can be roughly judged by observing the details of the image.

1.2 apl range is wide enough.

Apl, that is, the average level of images, is not paid much attention or familiar to by many engineers. However, if we encounter such a problem in some projects: when the video signal is transmitted through the optical terminal, when a large area of white appears in the picture (such as when the camera is illuminated by strong light), the picture on the monitor will appear horizontal jitter, then engineers must be familiar with it. This is because the apl range of video optical terminals produced by some manufacturers is too narrow. When there is a large area of white in the image signal, the DC component in each line of the image signal will increase, and the apl will increase, resulting in the decrease or loss of the amplitude of the line synchronization signal, and the display can not detect the line synchronization, resulting in picture jitter.

Step 2 consider the possibility

As a safety monitoring project, the first thing to consider is the availability of equipment. The availability of equipment must be considered by equipment manufacturers in product design, but some manufacturers may be unwilling or don't know how to do this work for some reasons. Here, the following problems are briefly discussed from the engineering point of view.

2. 1 The power supply is convenient and wide.

Power supply is the primary factor to ensure the availability of digital video transceiver, but it cannot be guaranteed to be available and reasonable. Talking about the availability of digital video transceiver has become a breeze. The video optical transceiver with 220vac power supply is more convenient and more reliable. The optical transceiver with 220vac power supply should be selected as far as possible in the project. At present, this optical transceiver mainly has two power supply modes, one is external power supply, and the other is internal power supply, that is, power supply and optical transceiver are integrated. From the perspective of engineering application, the built-in power supply is not only convenient to install, but also highly flexible, so most of the current multi-channel digital video optical terminals use the built-in power supply.

Based on the situation of domestic power grid and the reality of engineering site, we should try our best to choose multi-channel digital video optical terminals with wide input power supply range. Generally, optical terminals using switching power supply should be selected as far as possible. Compared with linear power supply, switching power supply not only has high efficiency, but also has a wide range of input voltage, which can basically ensure normal operation in the range of 160vac~265vac, and its output voltage will not change with the change of input voltage, so it will not affect the working performance and technical indicators of the optical terminal, nor will it cause repeated start-up of the optical terminal and interruption of the transmission of monitoring video and audio signals due to unstable power grid.

2.2 Strong adaptability to temperature and humidity.

In some security monitoring projects, the working conditions of optical transceiver are relatively bad, with a large temperature range and high air humidity. Some field monitoring points will occasionally lose power, the optical transceiver will generate heat when working, and there will be condensed water drops when the equipment is cooled down during power failure. All these require multi-channel digital video transceiver to pay more attention to the temperature range and allowable humidity, so as to ensure that it can work stably in harsh environment and meet the needs of security monitoring.

3. 1 The appearance is generous and the structure is reasonable.

Multi-channel digital video optical transceiver has high technology content, its appearance should be small, exquisite and elegant, and the overall structure must meet the requirements of engineering installation as much as possible. Generally speaking, indoor multi-channel digital video optical transceiver not only adopts 19 cable and allows viewing π Yao 19 cabinet, but also considers the need to place the optical transceiver on the desktop or wall in the project. In addition, the multi-channel digital video transceiver must also have good heat dissipation performance and electrical contact performance.

3.2 Rich interface and reasonable layout

In addition to adequate video interfaces, multi-channel digital video terminals can or may need to be equipped with other interfaces with rich functions, such as high-definition audio interface, ordinary telephone interface, asynchronous data interface, Ethernet interface and switch interface. This requires that the selected multi-channel digital video terminal must have the ability to upgrade the system, so as to avoid completely replacing the equipment due to network upgrade or system function change, thus protecting the user's upfront investment.

There are many kinds and quantities of interfaces of multi-channel digital video transceiver, and there may be some mode setting dip switches to match these interfaces. The user interface composed of all these elements should be reasonably laid out, with considerable operating space between interfaces, which is convenient for engineering installation and maintenance. For example, if the video interfaces are too dense, there will be an embarrassing situation that other normal video interfaces must be unplugged in order to repair a certain video interface in practical application.

3.3 The indicator light has a clear meaning, which is convenient for project opening and maintenance.

In order to facilitate the opening and maintenance of the project, the multi-channel digital video optical terminal should be marked with obvious indicator lights. The transceiver of multi-channel digital video optical transceiver must have video indicator besides power indicator to indicate whether the corresponding video channel has video signal input or output. Engineers and users can judge the opening and maintenance situation according to the instructions of the video indicator in the opening stage and maintenance stage of the project, locate the fault point and solve the possible problems as soon as possible.

In addition, for the audio and data parts, corresponding indicator lights should be provided. The simple way is to refer to the practice of telecom equipment, provide synchronization instructions and loop instructions, so that engineers and equipment manufacturers can judge whether the equipment system is faulty or the interface part is faulty, so as to make correct responses.

For Ethernet interface, connection/activity indicator, full duplex/half duplex indicator and 10m/ 100m indicator shall be provided according to the general requirements of data communication equipment.

Multi-channel digital video optical transceiver should also provide system indicator light to indicate whether the sending equipment is normal and whether the receiving equipment is normal, so that engineers can distinguish between equipment failure and optical fiber link failure.

To sum up, when selecting equipment, users can comprehensively consider the technical indicators, feasibility and practicability of the equipment, make various comparisons according to the above methods, and make appropriate plans according to the actual situation of the project, and finally find the most suitable multi-channel digital video optical terminal.