The basic knowledge that security monitoring must know

The "monitoring system" is one of the most widely used systems in security systems. Monitoring systems are generally composed of front-end cameras and back-end software systems. Currently, monitoring systems are widely used in major, medium, and small cities across the country. Many friends in the surveillance industry, especially those who have just entered the industry, have encountered some monitoring problems and have been confused. The following article shares the basics of monitoring and interpretation.

1) What is the meaning of CCTV? —— (Difficulty: Moderate)

A: CCTV is an abbreviation of English Closed Circuit Television, which means CCTV monitoring system.

2) What is the focal length of the lens? —— (Difficulty: Moderate)

A: From the optical principle, the focal length is the distance from the focal point to the center of the lens. The focal length. Such as "f=8-24mm," refers to the focal length of the lens is 8-24mm

3) What is the relationship between focal length and imaging size? —— (Difficulty: Easy)

A: The focal length is proportional to the imaging size. The longer the focal length, the larger the imaging. The shorter the focal length, the smaller the imaging. The focal length of the lens is inversely proportional to the size of the viewing angle, the longer the focal length, the smaller the angle of view, and the shorter the focal length, the larger the angle of view.

4) What is the relationship between the length of focal length and perspective? —— (Difficulty: Easy)

A: The focal length is inversely proportional to the depth of field. The longer the focal length, the smaller the depth of field, and the shorter the focal length, the greater the depth of field. The length of focal length is inversely proportional to the sense of perspective, the longer the focal length is, the weaker the perspective is, and the shorter the focal length is, the stronger the perspective is.

5) What is the camera's back focus adjustment? —— (Difficulty: Easy)

A: When the standard lens is installed, the image of the subject to be shot is exactly on the target surface of the CCD image sensor. A fixed lens can be used, and the method of adjusting the position of the ccd is called the rear focus of the camera.

6) What is the lens F value? —— (Difficulty: Easy)

A: The F value refers to the brightness of the lens. The <1.2> of the <maximum aperture ratio 1:1.2> shown in the lens specification is the F value. The smaller the F value, the higher the brightness of the lens. Each time the F value is reduced by the first-order distance, the brightness is increased by twice. The incident light amount of the lens is proportional to the cross-sectional area of ​​the light beam [the square of the effective aperture [D] of the lens], so the image brightness is inversely proportional to the square of the F-number. From this, it is estimated that the brightness is increased twice for each decrease in F-number.

7) What is the aperture of the lens? —— (Difficulty: Easy)

A: The function of the iris is like the rainbow of our human eyes. It is mainly used to adjust the amount of light entering the camera, F is the aperture of the lens, and the smaller F is the larger aperture

8) What is the depth of field? —— (Difficulty: Easy)

A: When an object is clearly focused, all scenes from a certain distance in front of the object to a certain distance behind it are also clear. The distance from front to back where the focus is quite clear is called the depth of field.

9) What is a wide-angle lens? (Wide Angle)——(Difficulty: Easy)

A: Since the wide-angle lens has a very short focal length, the scene projected onto the film becomes smaller and the angle at which the lens is shot is widened. In addition to shooting more scenes, it is possible to capture wide-angle images in a narrow environment. The viewing angle is more than 90 degrees, the observation range is relatively large, and the near image is deformed.

10) What is a telephoto lens? —— (Difficulty: Easy)

A: Within 20 degrees of viewing angle, the focal length can reach tens of millimeters or hundreds of millimeters

11) What is a zoom lens? —— (Difficulty: Easy)

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

12) What is optical zoom? —— (Difficulty: Easy)

A: It is based on the optical lens structure to achieve zoom, that is, through the lens movement to enlarge and reduce the need to shoot the scene, the greater the optical zoom, the more distant the scene can be shot

13) What is a three variable lens? —— (Difficulty: Easy)

A: The aperture, focus, and focal length need to be adjusted

14) What is a two variable lens? —— (Difficulty: Easy)

A: Usually an auto-iris lens with focus and focus adjustment

15) What is the lens video driver? (Video driver)——(Difficulty: Easy)

A: It sends a video signal and power from the camera to the lens to control the aperture on the lens. This video input lens contains an amplifier circuit to convert the video signal from the camera into the control of the iris motor.

16) What is the DC driver no Amp - (difficulty: easy)

A: It uses the DC voltage on the camera to directly control the aperture. This lens contains only a galvo diaphragm motor and there is no amplifier circuit in the camera. Two kinds of drive products are not interchangeable, but now there is a general-purpose automatic aperture lens

17) What is the difference between Type C and Type CS interfaces? —— (Difficulty: Easy)

A: The lens is equipped with two types, C-type and CS-type, and the C-type mounted lens has a 5mm more aperture adjusting the aperture value between the CCD camera and the lens. C-mount camera can use CS lens, but CS-mounted camera cannot use C lens

18) What is an aspheric lens? (Aspherical Lens)——(Difficulty: Easy)

A: The shape of the lens grinding is parabola, quadratic curve, cubic curve or high-order curve, and the correction factors such as lens aberration, chromatic aberration, spherical aberration, etc. are taken into account in the design, and usually one aspherical lens can achieve multiple spheres. The lens corrects the aberration effect, so the number of lenses can be reduced, so that the accuracy of the lens is better, the resolution is better, the color reproduction is more accurate, the light reflection in the lens is reduced, and the lens volume is also reduced accordingly. Aspherical lenses feature high magnification, short object distance, and large aperture. High magnification can simplify the type of lens, short object distance can be used in the occasion of close-range shooting, and large aperture can adapt to dark places, so the application field is becoming wider and wider. Japan AVENIA aspheric lens product SSV0770, close to 30cm

19) What is the relative aperture of the lens - (difficulty: easy)

Answer: In order to control the amount of light flux through the lens, an aperture is set at the rear of the lens. Assuming that the effective aperture of the aperture is d, due to the relationship of light refraction, the actual effective aperture of the lens is D, which is larger than d. The ratio of D to the focal length f is defined as the relative aperture A, that is, A=D/f, and the relative aperture of the lens is determined. The illuminance of the captured image, like the illuminance of the image, is proportional to the square of the relative aperture of the lens. Generally, it is customary to use F=f/D, which is the reciprocal of the relative light path to indicate the size of the lens aperture. The smaller the value of F, the larger the aperture, the greater the luminous flux reaching the CCD chip. Therefore, in the case of the same focal length f, the smaller the F value, the better the lens
 

20) What is CMOS technology? —— (Difficulty: Easy)

A: CMOS is called Complementary Metal-Oxide Semiconductor, and Chinese translation is complementary metal oxide semiconductor. The manufacturing technology of CMOS is no different from general computer chips. It mainly uses semiconductors made of silicon and germanium to make them coexist on the CMOS with N (band-electricity) and P (band + electricity) grades. Semiconductor, the current generated by these two complementary effects can be recorded and interpreted by the processing chip as an image

21) What is CCD - (Difficulty: Easy)

A: The CCD is called the Charge Coupled Device, which translates to "charge-coupled devices." It is made of a high-sensitivity semiconductor material that converts light into electric charge. Therefore, it has the advantages of high sensitivity, anti-glare, small distortion, small size, long life, anti-vibration and so on. The photosensitive element on it is called "pixel". The larger the number of CCD pixels and the larger the size of a single pixel, the clearer the image will be

22) What are the dimensions of the CCD chip? —— (Difficulty: Easy)

A: The image size of CCD is commonly used 1/2", 1/3" 1/4" The smaller the size of the camera can be made smaller. Under the same optical lens, the larger the imaging size, the field of view The larger the angle is, the larger the chip size is, the size of the imaging plane (width X height) Diagonal line 1/2 6.4x4.8mm 8mm 1/3 4.8x3.6mm 6mm

23) What is a HAD Sensor - (Difficulty: Harder)

A: The HAD (HOLE-ACCUMULATION DIODE) sensor is based on the N-type substrate, P-type, N + 2 polar body surface, plus positive pore accumulation layer, which is SONY unique structure. Due to the design of this positive hole accumulation layer, the dark current problem often found on the surface of the sensor can be solved. In addition, the vertical type tunnel through which electrons can pass is designed on the N-type substrate, so that the aperture ratio is increased, and the sentence is changed, which also increases the sensitivity. In the early 80s, Sony used its lead in variable speed electronic shutter products, and also obtained sharp images when shooting fast moving objects.
 

24) What is SUPER HAD CCD - (difficulty: harder)

A: The unit area of ​​the CCD is also getting smaller and smaller. The tiny lens technology can no longer enhance the brightness. If the magnification of the amplifier inside the CCD module is increased, the noise will be improved and the image quality will be significantly affected. . Sony furthered the research and development of CCD technology, improved the technology of using tiny lenses in the past, improved the light utilization rate, and developed the technology to optimize the shape of the lens, the Sony SUPER HAD CCD technology. Basically, the design that enhances the brightness by improving the efficiency of light utilization has laid the foundation for the current CCD basic technology.

25) What is the EXVIEW HAD CCD? —— (Difficulty: Easy)

A: The infrared light longer than the visible light wavelength can also be photoelectrically converted in the semiconductor silicon chip. However, until now, the CCD has not been able to collect these photoelectrically converted charges in an effective way into the sensor. For this reason, Sony's newly-developed "EXVIEW HAD CCD" technology in 1998 can effectively convert near-infrared light, which had not been effectively utilized before, into image data. The visible light range is extended to infrared light, allowing the brightness to be greatly improved. With the "EXVIEW HAD CCD" component, high-brightness photographs can also be obtained in a dark environment. Moreover, in the photoelectric conversion performed in the deep layer of the silicon crystal plate, the SMEAR component of the vertical CCD portion may leak out and may be collected in the sensor, so that the noise that affects the image quality is also greatly reduced.

26) What is a scanning system and what are those commonly used? —— (Difficulty: Easy)

A: The television format refers to the specific systems and technical standards adopted by a country's television system. Specifically speaking, there are currently three television formats in the world. At present, most countries in the world (including most European countries, Africa, Australia, and China) adopt the PAL system and adopt a frame rate of 25 fps; the United States, Japan, Canada, and other countries adopt The NTSC system established by the National Television Standards Committee (NTSC) uses a frame rate of 30fps (precisely 29.97 fps); the other SECAM system is mainly used in France, the former Soviet Union and Eastern European countries.
 

27) What is the working mode of the CCD camera? —— (Difficulty: Easy)

A: The image of the subject is focused on the CCD chip through the lens. The CCD accumulates a corresponding proportion of charge according to the light intensity. The charge accumulated by each pixel is moved outward by points under the control of the video timing. After filtering and amplifying, the charge is accumulated. , forming a video signal output. The video signal is connected to the video input of the monitor or television and the same video image as the original image can be seen

28) What is the camera's pixels? —— (Difficulty: Moderate)

A: Pixels are one of the most important indicators of camera CCDs. In general, higher pixel products have better image quality. But on the other hand, it is not that the higher the pixel, the better. For the same picture, the higher the pixel, the stronger the ability to analyze the image. In order to obtain high-resolution images or images, the amount of data it records is also large. Much more, the requirements for storage devices are much higher

29) What is the resolution of the camera? —— (Difficulty: Moderate)

A: Usually refers to the level of resolution, unless specifically designated as "vertical." The index for evaluating camera resolution is the horizontal resolution, which is the line pair, that is, the number of black and white line pairs that can be distinguished after imaging. Commonly used black and white camera resolution is generally 380-600, color is 330-540, the larger the value, the sharper the image is.

30) What is the camera's vertical resolution? (-(Difficulty: Easy)

A: The vertical resolusion is derived from the maximum number of horizontally interactive black and white lines.

31) What is the spectral response characteristic of the camera? —— (Difficulty: Moderate)

A: The CCD device is made of silicon material and is sensitive to near infrared. The spectral response can be extended to about 1.0um. The peak response is green (550 nm). When surveillance is performed at night during covert surveillance, near-infrared illumination can be used. The human eye can't see the environment, but it can be clearly imaged on the monitor. Since the surface of the CCD sensor has a transparent UV-absorbing electrode, the CCD is insensitive to ultraviolet light. There are red, green and blue filter bars on the imaging unit of the color camera, so the color camera is insensitive to infrared and ultraviolet.

32) What is the digital signal (DSP) processing of the camera? —— (Difficulty: Easy)

A: DSP (Digital Signal Processing) is an abbreviation for digital signal processing. Its working principle is to receive analog signals, convert them to digital signals of 0 or 1, and then modify, delete, and strengthen the digital signals, and interpret the digital data back to analog data or actual environment format in other system chips. Not only is it programmability, but its real-time operating speed can reach tens of millions of complicated instruction programs per second, and its source exceeds the general-purpose microprocessors. It is an increasingly important computer chip in the digital electronic world. Its powerful data processing capabilities and high operating speed are two of the most commendable features.

33) What is the camera's exposure? —— (Difficulty: Moderate)

A: Exposure is the image composition, the most primitive key factor. It is mainly determined by Aperture and Shutter.

34) What is the minimum illumination of the camera? —— (Difficulty: Moderate)

A: The minimum illumination is also called sensitivity. It is the degree of sensitivity of the CCD to ambient light, or the darkest light the CCD needs to image normally. The unit of illuminance is LUX. The smaller the value, the less light is needed and the more sensitive the camera is. The sensitivity of a black-and-white camera is about 0.02-0.5 Lux, and the color camera is more than 1 Lux. A 0.1Lux camera is used for ordinary surveillance applications; a 0.02Lux camera is recommended for use at night or when the ambient light is weak. When used with near-infrared lamps, low-light cameras must also be used

35) What is the Digital Zoom of the camera? (Difficulty: Easy)

A: Actually, the electronic zooming of the screen is to enlarge some of the pixels on the original CCD image sensor by using “interpolation” processing means. The pixel on the CCD image sensor is zoomed into the entire screen by an interpolation algorithm. With digital zoom, the captured scene is magnified, but its sharpness will be reduced to a certain degree, a bit like the ZOOM function in VCD or DVD, so digital zoom is not of great practical significance.
 

36) What is the Shutter of the camera - (Difficulty: Medium)

A: The shutter is a device that blocks light from entering the front of the lens. In general, the larger the time range of the shutter, the better. The low number of seconds is suitable for shooting objects in motion. A certain camera emphasizes that the shutter can reach 1/16000 seconds at the fastest, and can easily catch the target of rapid movement. But when you want to shoot at the night, the shutter time will be elongated. The silky water effect in common photos also needs to be shot with a slow shutter speed.

37) What is Optical Zoom? —— (Difficulty: Easy)

A: Digital cameras rely on optical lens structures for zooming. The digital camera's optical zoom mode is similar to that of a traditional 35mm camera. It is through the movement of the lens to zoom in and zoom out the scene to be shot. The larger the optical zoom factor, the farther the scene can be shot.

38) What is the camera's white balance? (White Balance, W/B) - (Difficulty: Medium)

A: The color of the object will change due to the color of the projected light. Photographs taken in different light situations will have different color temperatures. For example, photographs taken in a lighting environment with tungsten light bulbs (light bulbs) may be yellowish. In general, CCDs have no way of automatically correcting light changes like the human eye. Therefore, by correcting the white balance, it will immediately adjust the intensity of the red, green and blue colors of the entire image according to the image quality in the current image to correct the error caused by the external light. Some cameras also provide manual white balance adjustment in addition to designing automatic white balance or a specific color temperature white balance function

39) What is the camera's automatic white balance - (Difficulty: Medium)

A: The white balance setting will be continuously adjusted as the temperature of the object's color scene is changed, ranging from 2800 to 6000K. This method is most suitable for situations where the color temperature is constantly changing during shooting, so that the color is natural, but continuous white balance cannot produce the best color effect when the scene has little or no white color.

40) What is a camera r (Hummer) correction - (Difficulty: Medium)

A: The so-called Hummer correction is to detect the dark part and the light part of the image signal, and increase the ratio between the two, thereby improving the image contrast effect.

41) What is the camera's background light compensation (BLC) - (difficulty: medium)

A: Black Light Compensation Invisible Light Compensation, Backlight Compensation Generally, the camera's AGC operating point is determined by averaging the entire field of view, but if the field of view contains a very bright background area and a very dark foreground The target, then the AGC working point determined at this time may not be suitable for the foreground target, and the background light compensation may improve the foreground target display condition. When the background light compensation is on, the camera only averages one sub-area of ​​the entire field of view to determine its AGC working point. If the foreground target is located in this sub-area, the visibility of the foreground target is expected to improve.
 

42) What is the camera's automatic gain control (AGC)? —— (Difficulty: Moderate)

A: The automatic Gain Control automatic gain control automatic gain control camera output video signal must reach the TV transmission standard level of 0.7V, that is, in order to be able to output standard video signals under different scene illumination conditions, must make the amplifier The gain can be adjusted over a wide range. This gain adjustment is usually done automatically by detecting the average level of the video signal. The circuit that implements this function is called an automatic gain control circuit, abbreviated as AGC circuit. The camera with AGC function will improve the sensitivity in low illumination, but the noise will be more obvious at this time. This is because the signal and noise are amplified at the same time

43) What is the camera's signal-to-noise ratio (S/NRatio) - (difficulty: harder)

A: Signal-to-Noise Ratio signal to noise ratio, signal to noise ratio is the ratio of signal voltage to noise voltage, usually represented by the symbol S/N. Since in general the signal voltage is much higher than the noise voltage, the ratio is very large and the unit of signal-to-noise ratio is expressed in DB. The signal-to-noise ratio given by the general camera is the value when the AGC (automatic gain control) is turned off, because when the AGC is turned on, the small signal is boosted, so that the noise level is also increased accordingly. The typical signal-to-noise ratio is 45~55db. If it is 50db, there is a little noise in the image, but the image quality is good. If it is 60db, the image quality is good and no noise occurs. . The typical value is 46db. If it is 50db, there is a little noise in the image, but the image quality is good. If it is 60db, the image quality is good and no noise occurs.

44) What are the common synchronization methods? What is the difference between? —— (Difficulty: Easy)

A: The common methods are: internal synchronization and external synchronization. External synchronization includes: power synchronization, composite video synchronization, etc.

45) What is the camera's vertical sync? ——(Difficulty: Harder)

A: Vertical synchronization is the easiest way to synchronize two cameras. The vertical drive frequency ensures that the video can use the old switching period or four-segment machine to display several image sources on the same monitor. The vertical drive signal is usually composed of pulses with a repetition rate of 20/16.7 ms (50/60 Hz) and a pulse width of 1 to 3 ms.

46) What is color video composite signal synchronization? ——(Difficulty: Harder)

A: Color video composite signals Synchronous color video composite signals represent video and color trigger signals, meaning that the camera can synchronize with an external composite color video signal. However, despite the so-called color video composite signal synchronization, only horizontal synchronization and vertical synchronization are actually performed without color trigger synchronization.

47) What is the camera's internal synchronization - (difficulty: medium)

A: The internal synchronization is performed by the synchronization signal of the camera's internal synchronization signal generating circuit.

48) What is the external synchronization of the camera? —— (Difficulty: Moderate)

A: Use the external synchronization signal, power supply or sync signal generator to send the sync signal to the camera's external sync input. The VD sync pulse input on the camera signal cable completes the external VD synchronization. Synchronization of multiple cameras externally synchronizes multiple cameras so that each camera can work under the same conditions. Because each camera is synchronized, even if one camera is switched to other scenes, the picture of the synchronous camera will not be distorted.

49) What is the camera's DC line lock? ——(Difficulty: Harder)

A: DC line locking is an old technology that uses a DC 50/60 Hz power line current to synchronize the camera. Because DC 24V power is widely used in most building fire alarm systems, it is very easy to obtain. Since the old model of the switch and the segmentation system do not have a digital memory function, in order to maintain a stable image, the synchronization between the cameras is very necessary. The DC line lock is that the camera synchronizes to the AC 50/60 Hz.

50) What is LINE LOCK? ——(Difficulty: Harder)

A: LINE LOCK is a synchronization method that uses AC power to lock the sync pulse of the camera field. When the image is disturbed due to AC power, set this switch to the position of the line lock synchronization (LL) to eliminate the AC power interference.

51) What is an ultra-wide dynamic camera? —— (Difficulty: Moderate)

A: Ultra-wide dynamics is a feature that allows the camera to see images under very strong contrast. A wide dynamic camera is more than a dozen times larger than a camera with a traditional 3:1 dynamic range. Natural light ranges from 120,000 Lux to 0.00035 Lux at night. When the camera looks out of the window from the room, the indoor illumination is 100 Lux, while the outside scenery may have an illumination of 10,000 Lux. The contrast is 10,000/100=100:1. This contrasting eye can be easily seen because the human eye can handle a contrast ratio of 1000:1. However, traditional closed-circuit surveillance cameras can deal with it with great problems. Traditional cameras have only a 3:1 contrast performance. Choose to use the 1/60 second electronic shutter to get the correct exposure of the indoor target, but the outdoor image will be cleared (all white); or alternatively, the camera select 1/6000 second to get the perfect exposure of the outdoor image, but the indoor The image will be erased (all black)

52) What is the camera's peak sensing mode? —— (Difficulty: Moderate)

A: The peak-sensing mode uses the average value of the image instead of the entire image to determine the exposure index. Users of the rule system can respond to the most demanding requirements, such as capturing a white-spot image in the dark and seeing this. Little bright white details and colors

53) What is colorless scrolling? ——(Difficulty: Harder)

A: The digital signal processor video camera can only produce serious color scrolling images when used under fluorescent lighting. The image will change from white to blue, pink to white, and so on. This is because of the problems caused by AC power running at 50/60 Hz. The white light bulb provides stable light, and the fluorescent light fluctuates at 8.3 ms due to the intensity and color of the alternating current. The traditional camera calculates the white balance needs 100~150ms (0.1~0.15), slower than alternating current 8.5ms, so can never catch up. Clear color scrolling can occur for 8 shots of the current image

54) What is motion detection? —— (Difficulty: Easy)

A: Motion detection The entire monitoring screen is divided into multiple small areas. The user can arbitrarily select the area in the area and can set the sensitivity level of 1-20 levels for the selected monitoring area. In this way, when something moves, it will be detected by the camera server while recording

55) What is the camera's low-light camera? —— (Difficulty: Easy)

A: Because the general camera has poor monitoring performance at night with poor lighting conditions, poor illumination is an important indicator of the camera. The general camera's low-lightness indicators are below 0.5Lux for color and below 0.05Lux for black and white. The amount of illumination can be as low as not only depends on the aperture size (F-number) of the lens, but also depends on the conditions under which the indicated LUX value appears. In terms of the aperture size (F value), the larger the aperture, the smaller the F value it represents and the lower the required illumination.
 

56) What is an integrated camera? —— (Difficulty: Easy)

A: The integrated camera refers to an integrated camera with built-in lens and automatic focusing. There are many kinds of integrated cameras, and the current market players can be divided into color high-resolution type and day/night conversion type, which can be multiplied by 16, 18, 20, 22, 27 times. In general, the trend of all-in-one machines is that the illumination is getting lower and lower and the multiples are getting higher and higher.

57) What is a webcam? —— (Difficulty: Easy)

A: The network camera is a new generation camera that combines the traditional camera and network technology. It can transmit the image through the network to the other end of the network connection port, and the remote viewer does not need to use any professional software. A standard web browser (such as “Microsoft IE or Netscape”) can monitor its images.The webcam has an embedded chip that uses an embedded real-time operating system.The video signal sent from the camera is digitized and compressed by a highly efficient compression chip. The bus is transmitted to the web server, users on the network can directly use the browser to view the camera image on the web server, and the authorized user can also control the camera pan/tilt lens operation or operate the system configuration.

58) What is the camera head? —— (Difficulty: Easy)

A: The PTZ is a mounting platform consisting of two AC motors that can move horizontally and vertically.

59) What are the classifications of PTZ? —— (Difficulty: Easy)

A: According to the use of the environment is divided into indoor and outdoor type, the main difference is that the outdoor type sealing performance, waterproof, dustproof, large load. The installation method is divided into side loading and hoisting, which is to install the pan/tilt on the ceiling or on the wall.

The shape is divided into common type and ball type. The ball type PTZ is placed in a hemispherical, spherical protective cover, in addition to preventing dust from disturbing the image, but also hidden, beautiful, fast

60) What is the camera's protective cover? —— (Difficulty: Easy)

A: The device used to protect the camera is called a protective cover
 

61) What are the functions and functions of PTZ? —— (Difficulty: Easy)

A: There are indoor and outdoor points, the main role of indoor protective cover is dust; and the outdoor protective cover in addition to dust, the more important role is to protect the camera in a more hostile natural environment (such as rain, snow, low temperature, high temperature, etc. ) Work under. This not only requires a strict sealing structure, but also has a wiper, shower device, etc., as well as a function of temperature increase and temperature decrease. This determined that the price of the outdoor protective cover is much higher than the indoor protective cover. When selecting the protective cover, it should also be noted that the nominal size of the protective cover is the same as the nominal size of the camera. If it is difficult to be consistent, a large size protective cover can be used with a small size camera;

62) What is the bracket and classification of the camera? —— (Difficulty: Easy)

Answer: The parts used to fix the camera are wall-mounted, suspended, and other types. The choice of bracket is relatively simple, as long as its load capacity is greater than the total weight of the equipment installed on it, otherwise it will easily cause the bracket deformation, pan and tilt when the rotation, affect the monitoring image quality

63) What is a cloud mirror control decoder? —— (Difficulty: Easy)

A: The decoder is a device that converts the control signal from the front end into a voltage signal to control the pan/tilt and the lens.

64) What is a coaxial cable? —— (Difficulty: Easy)

A: The name of COARIAL CABLE is related to its structure. Coaxial cable is also one of the most common transmission media in surveillance. The pair of conductors it uses to transmit information is selected according to a layer of a cylindrical outer conductor set outside the inner conductor (a fine core) and the two conductors are isolated from each other by an insulating material. The outer conductor is The center axis of the center axis is on the same axis, so it is called a coaxial cable and the impedance is 75 ohms. The reason why the coaxial cable is designed in this way is to prevent the transmission of abnormal signals from external electromagnetic interference.

65) What is the transmission distance of the coaxial cable? —— (Difficulty: Easy)

A: According to the basic requirements of China's PAL-D video distortion, the measured value of transmission line without compensation transmission distance is: 75-7 coaxial cable is about 200-250 m, 75-5 is about 100-150m

66) What are the specifications of coaxial cable? —— (Difficulty: Easy)

A: The domestic coaxial cable has SYV75-3, SYV75-5, SYV75-7, SYV75-9 and other specifications

67) What is twisted pair transmission? —— (Difficulty: Easy)

Answer: Twisted Pair Wire (TP: Twisted Pairwire) is the most commonly used transmission medium in integrated cabling engineering. The twisted pair consists of two copper conductors with an insulating protective layer. Twisting two insulated copper conductors at a certain density can reduce the degree of signal interference, and the electric wave radiated by each conductor during transmission can be cancelled by the electric wave emitted from the other conductor. Twisted pair generally consists of two 22-26 insulated copper conductors. Its characteristic impedance is about 100Ω, and the distributed capacitance is about 15pF/m. Different from the coaxial cable, the signal is transmitted in a balanced manner in the twisted pair. With the use of twisted pair video transmission equipment and twisted pair, it can be guaranteed. High-quality transmission of video signals within a distance of 1.5Km

68) What is IP video surveillance? —— (Difficulty: Easy)

A: IP is an abbreviation for Internet Protocol. It is one of the most commonly used protocols for communicating over computer networks. IP monitoring solution is to transmit video information in digital form through wired or wireless IP network. As long as the network is reachable, video surveillance and recording can be realized, and this monitoring can be perfectly combined with many other types of systems.

69) What is a video amplifier? —— (Difficulty: Easy)

A: Video amplifier When the video transmission distance is relatively long, it is better to use a video line with a thicker wire diameter, and at the same time, the signal amplifier can be increased in the line to enhance the signal strength to achieve long-distance transmission. Video amplifiers can enhance the video's brightness, chroma, and synchronization signals, but intra-line interference signals can also be amplified. In addition, too many video amplifiers cannot be connected in series in the loop, otherwise saturation may occur, resulting in image distortion.

70) What is the RS-232 serial interface standard? —— (Difficulty: Easy)

Answer: RS-232 is the most widely used serial interface in the PC and communications industries. RS-232 is defined as a single-ended standard that increases the communication distance in low-rate serial communications. RS-232 adopts unbalanced transmission, so-called single-ended communication

71) What is the RS-422 interface standard? —— (Difficulty: Easy)

Answer: RS-422, RS-485, data signals using differential transmission, also known as balanced transmission. The full name of the RS-422 standard is "Electrical Characteristics of a Balanced Voltage Digital Interface Circuit", which defines the characteristics of the interface circuit. RS-422 four-wire interface. There is actually a signal ground, a total of 5 lines. The maximum transmission distance is 4000 feet (about 1219 meters) and the maximum transmission rate is 10Mb/s. The length of the balanced twisted pair is inversely proportional to the transmission rate. Below 100 kb/s, it is possible to reach the maximum transmission distance. The highest rate transmission can only be achieved at a short distance. The maximum transmission rate that can be obtained on a typical 100-meter long twisted pair is only 1 Mb/s. RS-422 requires a terminating resistor and requires its resistance to be approximately equal to the characteristic impedance of the transmission cable. In the moment distance transmission, no termination resistor is needed, that is, the termination resistor is generally no longer than 300 meters. The termination resistor is connected to the farthest end of the transmission cable

72) What is the RS-485 interface standard? —— (Difficulty: Easy)

A: RS-485 is based on RS-422, so RS-485 many electrical specifications and RS-422 similar. If you use balanced transmission methods, you need to connect termination resistors on the transmission line. RS-485 can use two-wire and four-wire, two-wire system can achieve real multi-point two-way communication. RS-485 differs from RS-422 in that its common-mode output voltage is different, RS-485 is between -7V and +12V, RS-422 is between -7V and +7V, RS-485 receiver The minimum input impedance is 12k ohms and RS-422 is 4k ohms; RS-485 meets all RS-422 specifications, so RS-485 drivers can be used in RS-422 networks

73) What are the similarities and differences between RS-422 and RS-485? —— (Difficulty: Easy)

A: RS-422, RS-485, data signals using differential transmission, also known as balanced transmission.

RS-422 four-wire interface. There is actually a signal ground, a total of 5 lines. RS-485 adopts two-wire mode and two-wire system can realize true multi-point two-way communication. RS-485 differs from RS-422 in that its common-mode output voltage is different

74) What is a video switcher? —— (Difficulty: Easy)

A: The video switcher is a key device on the main console in the control center. It is a device that selects video image signals. Simply put, several video signals are input, and by controlling them, one of the video signals is output. In a television monitoring system composed of multiple cameras, it is generally not necessary to use a monitor having the same number of cameras to display the image signals of each camera one to one.

75) What is a multi-screen controller? —— (Difficulty: Easy)

A: Using image compression and digitization methods, several pictures are compressed in the same proportion on the screen of a monitor. Some also have a built-in sequence switcher function, which can display the full-screen images of each camera input in turn on the monitor in the order and interval time (as if the host switches the screen in turn), and can use the video recorder according to the above The sequence and time interval are recorded. The interval time is generally adjustable. With sequence switching, picture-in-picture, multi-picture output playback video display, interconnected camera alarm display, touch-type pause screen, alarm record playback, time, date, title display and other functions

76) What is a video distributor? VDA (Video Distruuting Amplifier) ​​- (Difficulty: Easy)

A: A splitter is the most commonly used component of a distribution network in a cable television transmission system and is used to distribute signal components. Its function is to equally divide an input signal into several outputs, usually two, three, four, six, etc.

77) What is video switching control - (Difficulty: Easy)

Answer: The central processing module of the matrix system controls the video switching of all camera inputs and monitor outputs. The switching can be controlled by the operation of the keyboard, the execution of the system switching queue, or the automatic response function of the alarm.

78) What are the system switching methods of the matrix system? —— (Difficulty: Easy)

A: The matrix system switching can be divided into five kinds of system switching methods: free switching, program switching, synchronous switching, group switching and alarm switching.

79) What is the free switching of the matrix system? —— (Difficulty: Easy)

A: A free switching queue is to program a group of camera inputs to be displayed on a monitor. Each camera screen can stay at different times, each monitor has its own switching queue

80) What is the program switching of the matrix system - (difficulty: easy)

A: Multiple queues can be run on any monitor by the operator or by a timer call at any time. Each group of switching queues can consist of multiple cameras and their presets, dwell time, and auxiliary switch actions. In a group of switching, the same camera picture or multiple auxiliary actions of one camera can appear multiple times

81) What is the synchronous switching of the matrix system - (difficulty: easy)

A: A synchronous switching queue refers to the sequential switching of a group of camera pictures to a group of continuous monitors. Each system synchronous switching queue consists of multiple cameras and their presets, dwell time, and auxiliary switch actions

82) What is a matrix system group switch? —— (Difficulty: Easy)

A: A group switching queue means that a group of system synchronization switching queues are automatically and sequentially switched to display on multiple groups of continuous monitors. Each system group switching queue consists of multiple system synchronization switching queues

83) What is the alarm switch? —— (Difficulty: Easy)

A: The system alarm switching queue refers to the system switching the camera screen to the arming monitor when receiving the alarm signal. Each alarm switch can link the camera image and its preset point, auxiliary switch

84) What is the alarm response (alarm linkage function)? —— (Difficulty: Easy)

A: The alarm consists of the contact signals from the alarm devices connected to the matrix system. The matrix host system has multiple independent alarm contacts (including extended alarm contacts) that can be programmed to switch the camera input to the monitor or make an auxiliary output when an alarm is received.

85) What is the priority level of authority? —— (Difficulty: Easy)

A: Multiple priority levels, designated keyboards and users allow high-priority users to control cameras without responding to low-priority users, each with priority restrictions

86) What is the sub-control of the matrix system? —— (Difficulty: Easy)

A: Usually refers to the control and observation terminal equipment set up outside the central monitoring room

87) What is a character stacker? —— (Difficulty: Easy)

A: The time, date, and character overlays are devices that are widely used in television monitoring systems. They can incorporate time and date information and camera identification information (usually the geographic position of the picture taken by the camera) into the video signal. The user can not only see the camera screen on the monitor screen, but also can see the time and date information and the camera identification characters superimposed on the screen. These characters can be saved together with the image content after being recorded by the video device, which is the future Review provides great convenience

88) What is full duplex? —— (Difficulty: Easy)

A: At the same time, it can be sent and received. Full-duplex requirement: Receive and send separate channels, can be used to achieve communication between two stations and star network, ring network, can not be used for bus network

89) What is half duplex? —— (Difficulty: Easy)

A: Half duplex: It is impossible to send and receive at the same time. Half-duplex requirements: transceivers can share the same channel, LANs that can be used in various topologies are most commonly used in bus networks, and half-duplex data rates are theoretically half that of full duplex.

90) What is the difference between a monitor and a TV? Why can't the TV be used as a monitor? —— (Difficulty: Easy)

A: The monitor is functionally simpler than the TV, but in terms of performance, it requires higher requirements than the TV. The main difference is reflected in the three "degrees".

1) Image sharpness: Since the traditional TV receiver receives the RF signal transmitted by the TV station, the bandwidth of the video image corresponding to this signal is usually less than 6M. Therefore, the definition of the TV is usually greater than 400 lines, which requires the monitor to have a relatively high resolution. High image resolution, so the professional monitor should have a bandwidth compensation and boost circuit on the channel circuit compared to the traditional TV, making the passband wider and the image sharper.

2) is the degree of color reproduction, if it is said that the definition is mainly determined by the amplitude characteristics of the video channel, the reduction is mainly from the monitor red (R), green (G), blue (B) three primary colors The phase signal is determined by the phase of the luminance signal. Since the monitor usually observes static images, the requirement for the color reproduction of the monitor is higher than that of the television. Therefore, the channel for the viewing channel of the professional monitor should have the brightness, color processing, and R, G, and B processing. Accurate compensation circuit and delay circuit to ensure phase synchronization of light/color signals and R, G, B signals

3) It is the stability of the whole system: When the monitor is configured as a closed-circuit monitoring system, it usually needs 24 hours a day, 365 days of continuous and continuous power-on use (while the TV usually only works a few hours per day), and some monitors The application environment may be rather harsh, which requires a higher reliability and stability of the monitor. Compared with televisions, in terms of design, the monitor's current, power consumption, temperature and resistance to electrical interference, the ability and margin of electric shock, and the average time between failures are much longer than those of TV sets. At the same time, the monitor must also The use of a fully shielded metal shell ensures electromagnetic compatibility and interference performance; in the selection of components, the characteristics of the components used in the monitor, such as voltage resistance, current, temperature, and humidity, are higher than those used in televisions; In the installation and debugging, especially the components and the aging process requirements, the monitor's requirements are also higher, the aging of the whole TV set is usually power on the assembly line at room temperature for about 8 hours, and the whole monitor Aging requires aging for more than 24 hours in the aging pipeline of a high-temperature, high-humidity confined environment to ensure the stability of the entire machine.

From the above analysis, if you use a TV as the monitor of the monitoring system, the components used in the TV are not suitable for use, except that you may feel that the image is blurred (lower definition and poorer color reproduction). Intermittent continuous use requirements. If forced to use the TV as a monitor. It is easy to cause troubles when it is light, and it may cause accidents due to the high working temperature of the TV when serious.

91) What is an interlaced monitor and a progressive monitor? —— (Difficulty: Easy)

A: Interlaced and progressive lines mainly refer to the way the monitor tubes are scanned

Interlaced scanning refers to dividing an image into two fields for scanning. The first field (odd field) scans for odd lines such as 1, 3, 5, and the second field (even field) scans for even lines such as 2, 4, and 6; It forms a complete image (ie, a frame). So for the PAL system, scanning 50 fields per second, the field frequency is 50HZ, and the frame frequency is 25HZ; for NTSC, the field frequency is 60HZ, and the frame rate is 30HZ, although in the human visual screen reappears It is a continuous image, but even field switching will cause the screen to flicker and the effect of obvious line spacing due to the odd number of occasions.

Progressive scan refers to the scan line in the order of one-by-one scan. Interlaced monitors have the disadvantages of poor image quality, low resolution, large noise, and serious image flickering. The progressive scan monitor is designed to eliminate the defects of interlaced scanning, converting analog video signals to digital signals, and using digital color decoding to achieve repetitive use of one line or one signal by means of digital signal storage and control technology (ie, low-speed reading, High-speed readout) 50HZ progressive scan, or increase the frame rate, to achieve 60HZ, 75HZ so 85HZ progressive scan mode. Progressive scanning technology converts input signals into digital video signals through A/D conversion, and then performs digital line decoding and digital image processing circuits to perform line and field scan processing. The channel bandwidth is greatly improved (up to 10 MHz - 20 MHz) and the definition is greatly improved. The noise is greatly reduced, while the progressive display eliminates line spacing and inter-line flicker, while the increase in frame rate (eg, 60 Hz to 85 Hz) reduces or eliminates large area image flicker. Therefore, when the line-by-line monitor came out, it was very popular among users. Of course, since the progressive monitor uses one line or one field for repeated use, the line frequency is doubled from the interlace, from 15625HZ to 31250HZ, and the 75Hz line-by-line line frequency is 46875Hz. After the line frequency is increased, the stability and reliability of the output stage will be severely tested, and the overall design and manufacturing costs will be greatly increased, so the overall price is higher.

92) What is a star camera? —— (Difficulty: Easy)

A: Starlight CCD cameras have photons on the CCD sensor that are 2 to 128 times (1 to 2 seconds) longer than the maximum exposure time of a normal CCD camera (1/60 or 1/50 second). As a result, the minimum illuminance at which the camera produces usable images is reduced by 2 to 128 times. Using a star camera with a frame-accumulation technique, users can see color images under the conditions of the illuminance of stars (0.0035 Lux), and see the black-and-white images under the cloudy illuminance conditions (0.0002 Lux), and the scattered background light in the city ( Such as light pollution) enough to produce a good color exposure

93) What is a 100Hz monitor? —— (Difficulty: Easy)

Answer: In order to overcome the defects of large noise and image flicker in the 50HZ interlaced monitor, the 100Hz interlace scanning is achieved by means of a double field, which causes the illusion of human vision and masks the defects of large area flicker. Currently, chip manufacturers have not developed 100Hz progressive technology and chips. The nominal 100Hz monitor on the market can only be a 100Hz interlaced monitor.

94) What is composite video? (CVBS)——(Difficulty: Easy)

A: It is the most common input signal for general video recorders or video cameras, and it is also the most common input signal. Signal size is 1 Vp. Input impedance: 75 Q and Hi

95) What is the S terminal output? (S-video)——(Difficulty: Easy)

A: The full name of the S-Video is Separate Video, also known as SUPER VIDEO. The S-Video connection specification is a specification developed by the Japanese, and S refers to "SEPARATE (separation)", which separates luminance and chrominance output, avoiding mutual interference of luminance and chrominance when the hybrid video signal is output. The S terminal is actually a five-wire interface consisting of five core lines, two luminance signals, two video color signals, and a common shielding ground.

96) What is a soft compression video card? —— (Difficulty: Easy)

答：软压缩录象卡，主要是由一个若干个图象采集芯片为核心，配合周边电路与元件，完成图象采集功能的一种硬件电路板产品，软压缩录象卡从外型上看，各厂家做的基本一样，差别很小，因为各厂家设计电路是都必须按照芯片资料提供的样板电路为基础而设计软压缩录象卡的图象采集是通过图象采集芯片(如FUNSION 878A)完成，而图象压缩则是通过软件实现，即通过电脑CPU运算完成

97)什么是硬压缩录象卡？ —— (Difficulty: Easy)

答：硬压缩录象卡，其图象采集与图象压缩都是通过板卡上的芯片实现。与软压缩的区别主要就是该产品将图象压缩算法软件写入了硬件板卡上的DSP芯片里，让DSP代替CPU来运算，减轻了CPU运算的压力，如果您的硬盘录象机电脑主机CPU频率低，监控路数多，而且要求全实时，硬盘空间特别大的话可采用硬压缩录象卡

98) 什么是嵌入式硬盘录像机？(IDVR )——(难度：容易)

答：指操作系统和功能软件集成于计算机硬件系统之中。简单的说就是系统的应用软件与系统的硬件一体化，类似与BIOS的工作方式。具有软件代码小，高度自动化，响应速度快等特点。特别适合于要求实时的和多任务的体系

99)什么是工控式硬盘录像机？ —— (Difficulty: Easy)

答： 工控式硬盘录像机(PC-BASED DVR)以工控机为基础硬件，以WINDOWS操作系统为基础软件，配备视音频压缩板卡，借助于专业压缩算法以及PC机软硬件能力实现对监控系统视音频信号进行记录和回放的设备。工控式DVR的核心设备是视音频压缩卡

100)什么是色调？ —— (Difficulty: Easy)

答：是当人眼看到一种或多种波长的光时所产生的彩色感觉，它反映颜色的种类，是决定颜色的基本特性，如红色、棕色就是指色调