Building intercom

Security protection system

Building intercom is a security system. It is a management system, commonly known as building intercom system, that realizes the communication between visitors, residents and property management center in multi-storey or high-rise buildings, carries out information exchange and realizes the safe access control of the community.
Visitors can conveniently call the residents and talk with them through the host computer in front of the downstairs unit, and call the property management personnel to help open the unit door without the key. The residents can also control the opening and closing of the unit door inside, and the residents can operate the indoor extension to call the property management personnel. The door host this can also receive the resident alarm signal at any time to the host on duty to notify the community security personnel, the system not only enhances the high-rise residential security work, but also greatly facilitates the residents, reduce a lot of unnecessary upstairs and downstairs trouble, communication is more convenient, fast and safe and reliable.

Working mode

The door of the building is always locked at ordinary times to avoid non-building personnel entering the building without permission. The occupants of the building can freely enter and exit the building with keys. When a guest comes to visit, the guest needs to press the room number of the guest on the keyboard of the intercom host outside the building door and call the intercom extension of the guest. The owner of the visited household makes two-way or video call with the visitor through the intercom device and confirms the identity of the visitor through the visitor’s voice or image. After confirming that visitors can be allowed to enter, the owner of the resident uses the unlocking button on the intercom to open the electronic lock on the entrance door of the building and the visitors can enter the building. When visitors enter the building, the door automatically locks.
Residential area property management security department through the community security intercom management host, can monitor the work of each residential building security intercom system in the community. If the entrance door of a residential building is illegally opened, security intercom host or line failure, the community security intercom management master will send alarm signals, showing the content and location of the alarm. The property management department of the community and the residents or the residents can use the system to communicate with each other. For example, the property department notifies the residents to pay various fees, the residents notify the property management department to repair the residential facilities, and the residents call the management personnel of the community or the neighbors for help in case of emergency.

Basic structure

Building intercom system is mainly composed of door host, indoor extension, UPS power supply, electronic lock and door closing device. According to the type can be divided into direct press type, digital type, digital household access, visual intercom, non visual intercom and so on.

Doorway machine

The door host is the core part of the building intercom system control, each indoor extension transmission signals and electric lock control signals are controlled by the host, its circuit board using vibration reduction installation, and moisture-proof treatment, anti-vibration moisture-proof ability is very strong, and with night lighting device, beautiful appearance, generous.

Indoor unit

Indoor machine is a kind of intercom phone, generally with the door machine for intercom, household building intercom system with the door machine into a set of internal telephone system can complete the system of users in the telephone contact, more convenient to use, it is divided into visual indoor machine, non-visual indoor machine. With electric lock control function and monitoring function, generally installed at the door of the user’s home, the main convenience of residents and visitors to talk to each other.

UPS power supply

Its main function is to keep the building intercom system power. Normally, it is charged. When a power failure occurs, the UPS power supply is in the state of supplying power to the system. Building intercom system, manufacturers generally do not use UPS batteries, mainly visual system power consumption is too large, the general small capacity UPS battery can not ensure the use of time!

Door lock

Its internal structure is mainly composed of electromagnetic mechanism. As long as the user presses the electric lock key on the extension, the electromagnetic coil can be energized, so that the electromagnetic mechanism drives the connecting rod action, and the door can be controlled to open. It is a special automatic door closing connecting rod mechanism. It has a regulator, can adjust the acceleration and force of action, easy to use, flexible.

Development background

In the period when the intercom industry just entered China, affected by the national economy, the weak national awareness of security and other factors, the development of building intercom has been delayed, and the product has stayed in the non-visual intercom stage. Until the end of 90’s, black and white non visual talkback began to be favored by the majority of users, gradually into the talkback market. With the development of economy and the gradual improvement of national living standards, people have a higher pursuit of quality of life, which makes color visual intercom products ushered in the development of the spring. Nowadays, building intercom is developing towards integration, intelligence and information.
Convergent expansion space
At present, the semi-digital networking mode has been relatively common, that is, TCP/IP networking to the unit door machine, unit door machine to the household door machine and indoor machine is still using the traditional bus mode. It is understood that the reason is that TCP/IP networking in wiring, networking, signal transmission, system scalability, functional scalability, easy maintenance of the system, networking anti-interference, multi-channel communication ability and so on have obvious advantages.
Compared with the traditional bus analog walkback, the IP digital walkback has the following characteristics: transmission distance is not restricted by the region, the expansion and upgrading is very convenient; The transmission of audio and video, control signal effect is far better than the traditional bus; It can realize the integration of home alarm, home appliance control, remote monitoring, community service and other functions. Installation and debugging is convenient, shorten the project cycle, save the project cost.
Integrated application
Intercom system generally includes: central management machine, wall machine, unit door machine, secondary confirmation door machine, indoor extension, etc., through the private network networking. The basic functions of video intercom include two-way call, video call, door machine monitoring, remote unlocking and other functions. With the enhancement of development and the needs of users for additional functions, the intercom system also derives image capture storage function, leave a message function, call recording and video function, household access function, ladder control function, etc. And can be integrated with access control system, access control system through the IP network transparent transmission.
Domestic development trend
1, building intercom system formalized into a relatively independent industry sector
Although the development of building intercom system in China is not long, but because of its promising market prospects, the number of manufacturers has soared to about 250. Building intercom and TV monitoring, anti-theft alarm, access control management, intelligent parking lot together constitute the security industry. Due to the progress of society, the change of human life mode and thinking mode, coupled with the development of economy, the differentiation of social classes intensified, social security situation is not optimistic, all these have a great role in promoting the development of the security industry.
2. Increased sales, serious bidding industry, lower profit margin
A company in the building intercom industry, prices fell sharply at the beginning of the year. Although the behavior of bidding can increase the overall sales, but the profit is also greatly reduced. Some manufacturers realize that the bidding industry will bring no living space of serious consequences, so they are committed to improving product quality, increase the investment in after-sales service, accelerate the progress of product development, building intercom market segment gradually formed.
Building intercom system has been used in Europe and the United States, Hong Kong, Taiwan and other regions for nearly 20 years. Since 1992, foreign manufacturers of building intercom system have been developing the market in China. There are nearly 10 foreign brands in the mainland. The domestic building intercom enterprises are developing rapidly. The market share of the domestic building intercom system is about 80%


System capacity
The scale of Chinese residential districts is hundreds of families and thousands of families, and the buildings are the main ones, which is hard to imagine in western countries where the population density is relatively low. Therefore, the capacity of intercom system abroad is far less than ours.
Environmental requirements
The community developed by our country can only be regarded as a blank house. Most families have to be renovated after purchase. The decoration of each family will cause certain damage to the system, and the period of full occupancy of the community may be as long as several years. In view of this situation, the domestic powerful companies in the design of the system are to break and anti-interference in the first place.
System compatibility
Due to the different requirements of the occupants, the occupants of the same unit may have some installed visual, some requirements installed non-visual, some requirements do not need to network, but in the future to network, etc., all these put forward high requirements for system compatibility.

Key points of selection

First, stability: the stability of building intercom is crucial! Building intercom system design must be reasonable: all kinds of isolation protection measures must be in place, circuit design to be accurate and reasonable, which not only includes the design of components to be reasonable, the system software design to improve, stable! Secondly, the use of components, must use new electronic components, put an end to the use of second-hand, unstable components! The quality of components is also very important! Building intercom stability can be said: 60% is from the building intercom system itself; 30% from the construction environment and construction equipment selection; 10% from the use of building intercom electronic components!
Second, after-sales service: any product, there is no guarantee of 100% perfect! After-sales service is another crucial issue! Part of the use of second-hand components or defective manufacturers, are not willing to provide users with after-sales service, or drag on after-sales service, do not recognize such practices, such customers mainly rely on low prices to compete in the market! Therefore, we must find a good faith, technical strength of the production enterprise cooperation!
Implementation standard
Domestic standard
GA/T72-94 Technical Regulations for Intercom systems and electronic security doors in Buildings
GA/T72-2005 floor apartment intercom system and electronic security door general technical conditions
GAT678 network type visual intercom system technical requirements
GA/T269-2001 black and white video intercom system


The development of building intercom technology has experienced four stages
The development of intelligent community construction changes rapidly although it starts late in our country. With the popularization of Internet, many communities have realized broadband access, information highway has been laid to the community and into the family. The conditions for the intelligent cell system to adopt TCP/IP technology have been met. The running basis of intelligent cell system is changing from cell fieldbus to Internet, from decentralized management to centralized management.
The first generation
The earliest building intercom products have single function, only unit intercom function, since the end of the 1980s, the domestic has begun to have (4 n type) single household visual intercom and unit type intercom products appear. The system only uses the coding, decoding circuit or RS-485 to carry out the communication within a single building in a small area, and cannot realize the large area networking in the whole community. This decentralized control system is incompatible and independent, which is not conducive to the unified management of the community, and the system function is relatively simple. At that time, the market capacity is small, talkback products in Guangdong region have individual manufacturers, users concentrated in Guangdong. Video intercom products are mainly Korean, Taiwan brand, to one – to – one, in Shanghai Guangdong sales. The annual demand in the domestic market is less than 100,000 households.
From 1993 to 1997 was the first development period of the domestic market. Several professional manufacturers appeared in Guangdong area. These manufacturers began large-scale production of products and continuous progress of technology.
Second generation
With the increasing demand of domestic people, the original requirements of no networking and invisible can no longer be met, so it enters the stage of networking. In the early 1990s, most of the products were produced by Taiwanese brands, such as Kenridge. In the late 1990s, especially after 1998, networking became the most basic requirement of intelligent buildings. Therefore, the cell control network technology, widely used single chip technology field bus technology. Such as CAN, BACNET, LONWORKS and domestic AJB-BUS, WE-BUS and some use of RS-485 technology to achieve the bus and so on. Using these technologies, various scattered systems in the community can be connected, managed and coordinated, thus forming a relatively large regional system. The application of fieldbus technology in cell makes the intercom system take a big step forward.
Building intercom products have entered the second period of rapid development, large-scale community networking and comprehensive intelligent building intercom equipment began to emerge. After 2000, the demand for building talkback products in provincial capital cities developed rapidly, and the corresponding manufacturers also increased rapidly, forming the Pearl River Delta and the Yangtze River Delta two main manufacturers cluster; The Pearl River Delta is dominated by Guangdong and Fujian.
From the perspective of demand market, this product has entered the demand platform area. After a large number of applications, the traditional bus visual intercom system also shows some limitations, has not been able to meet the demand of our market.
◆ Poor anti-interference ability. The sound or image is often disturbed and unclear
Limited transmission distance. It is necessary to increase the video amplifier at a long distance, and it is difficult to network when the cell is large, and the cost is high
◆ The bus system technology, busy situation is especially, because the same audio and video bus only allows two households to talk, can not achieve household call
◆ Single function, most of the products are limited to call, unlock and other functions, equipment usage is very low
Due to technical limitations, it is difficult to upgrade or expand the function of the product
◆ Lack of industry standards, system integration is difficult, products between different manufacturers can not be interconnected, and visual intercom system is difficult to connect with other weak current subsystems
◆ Can not share the district integrated wiring, engineering installation is large, high service cost, can not be well integrated into the district integrated network
We cannot realize the comprehensive construction of the Internet of things in our country, so we cannot expand the pace of intelligent district.
In 2000, launched the network visual intercom system, control digital signals using network cable transmission, audio and video using coaxial cable transmission of the building intercom system, so wiring requires two sets of lines. This system breaks the traditional bus structure and provides the feasibility witness for the building intercom system to transition to the digital stage. Therefore, it belongs to 2.5 generation products, but it still cannot meet the later development.
The third generation
Multifunctional video intercom (LAN type)
From 2001 to 2003, with the popularization of Internet and the rapid development of computer technology, great changes have taken place in people’s work and life. The concept of digital and intelligent community has been accepted by more and more people. Building intercom products have entered the third high-speed development period, and multifunctional intercom equipment has begun to emerge. LAN technology development products based on ARM or DSP technology gradually launched, digital talkback technology has a breakthrough development! Using the network to transmit data, fuzzy the concept of distance, can be extended indefinitely. Breaking through the traditional concept, it can provide network value-added services (such as video phone, advertising and other functions, and the cost is low). Integrate the security system into the device to improve the utility of the device. The main advantages are:
◆ Suitable for complex, large-scale and super-large scale cell networking requirements
◆ Digital indoor unit realizes digital, voice, image transmission through a network cable, so that there is no need to deploy data bus, audio cable and video cable. As long as the digital indoor phone access to the indoor information point.
◆ Can realize multi-channel interworking at the same time, without the phenomenon of busy lines.
◆ It has a great impact on the middle and high-end market of the industry, and can develop across industries
Interface standardization, standardization of specifications
◆ Low network cost, easy to upgrade and expand
◆ Use the existing network, free from engineering construction
Easy to maintain and upgrade products
In fact, manufacturers of traditional products have also noticed these demands of the market and tried to meet some of them. However, with the continuous improvement of user needs, traditional manufacturers have felt powerless and have terminated the development of original product lines and turned to seek digital solutions. According to the market survey, the launch of digital products have a small number of domestic manufacturers have launched a series of products with multi-functional use of LAN technology. And it gets a good reaction in the market. Verify and determine the network technology in the visual intercom, as well as in the development of intelligent community positive role and inevitable trend.
The fourth generation
Free video intercom (Internet type)
By 2005, the WAN digital video intercom system of the real estate has quietly appeared nationwide, and its system stability, operability are very stable and reliable. Digital video talkback era has really come!
2004 to 2005, the market appeared digital video intercom system products. Wan video intercom system is constituted on the basis of internet WAN, digital indoor unit as a cell network terminal equipment plays two roles
. One is to use the digital indoor machine to realize the visual intercommunication of the community;
The other is to communicate with a visual IP phone or PC anywhere on the network through a cell Ethernet or Internet. As the whole industry enters a virtuous cycle, a brand new broadband digital industry chain is gradually becoming clear. Digital products based on broadband audio and video transmission and data transmission are new products extended by broadband basis (such as Anychat audio and video). It includes both broadband network operators and broadband user resident network access providers. In the future, broadband network content providers characterized by video interaction, broadband TV and other downstream industries are also emerging. In short, the main direction of the development of visual intercom products is digital, digital is the only way for the development of visual intercom system, digital construction will bring a new opportunity for the construction of intelligent information community.


According to the analysis, the main defects of the building intercom are as follows:
Anti – interference ability: anti – interference is the building intercom industry generally feel headache problem. In terms of product quality, anti-interference ability is urgent to be improved, especially in parts of thunderstorm prone areas. In the field construction, the improper selection of wire, wiring is not standard, etc., will also lead to various interference problems. Therefore need to cause the product supplier and the construction side of the general attention.
Signal attenuation: Usually video amplifier to solve the problem, but at the same time cause distortion problems. And if the wire selection is not appropriate, there will be signal attenuation.
Networking function: Both the bus and TCP/IP can be networked. Bus is still the mainstream, networking function is relatively simple, and transmission distance is limited, which is not good for large-scale networking.
Compatibility/standardization: The compatibility/standardization problem caused by the inconsistency of audio and video encoding and decoding algorithms, wiring standards, communication protocols and interfaces has been troubling the purchasers. This part still needs to be led by relevant departments to promote the formulation of relevant standards.
Audio and video transmission delay: Mainly in the TCP/IP networking mode, the manufacturer should continue to optimize the algorithm and other aspects, so as to obtain faster transmission speed and audio and video quality.
Noise control and echo cancellation: Mainly speech processing still requires vendor optimization algorithms, and the processor needs to provide more flexible and powerful speech support.
Integrate more functions: some users think that the intercom product can abide by the duties, the simpler the function is the better; Some users want to integrate more. In this regard, manufacturers should seek truth from facts and guide users’ purchasing consciousness correctly.
Humanized design: mainly refers to the humanized operation interface, including indoor machine, door machine, etc., the buyer hopes that the product operation as far as possible silly, so that children and the elderly are easy to understand and operate, such as: voice prompts in the operation process, family messages, etc.; The screen graphical interface is richer, rather than just text prompts and so on.
Better picture quality: mainly color intercom display clarity, color degree, saturation and other problems. In addition, according to the buyer’s response, some manufacturers in order to save production costs, choose some second-hand screens, developers and engineers do not know. It’s usually fine for a year, after which you might have to replace the screens altogether


Preparatory work
Building intercom repair is different from other electrical equipment repair, must know some necessary knowledge. I think it is important to understand the following aspects:
A. Name of the manufacturing enterprise, telephone number, installation time and installation company of the building intercom;
B. The wiring diagram and manual of the intercom system of the building, if any, should also be found together with the maintenance files;
The role of these two preconditions: to understand the production enterprise of the building intercom is to consult the technician of the production enterprise in the case of no one; Understand the installation company is to avoid unnecessary mistakes between peers, do not form vicious competition or artificial damage, understand the installation time is conventional damage to evaluate the problem; To understand the wiring diagram, instructions and maintenance files, naturally, is to complete the maintenance work faster and better.
Inspection tool
Screwdriver, multimeter, tape or heat shrink tube, 2 meters long 10 core sheath line, an adjustable power supply, spare electronic circuit motherboard provided by the manufacturer;
Conventional problem
Do not open the lock, can not hear, no image, can not talk, can not password unlocked, can not swipe card unlocked, indoor machine can not open the lock
Order of troubleshooting
First look at the electricity, then look at the wire, and finally test other functions!
Maintenance matters needing attention
All wiring and disconnecting operations must be powered off! (Easy to cause short circuit in the case of constant electricity)
Host problem
First, do not open the lock:
1. Any unlocking method other than the key shall not open the lock: first, please test whether both ends of the unlocking wire are properly connected, and then use a multiwatt-hour meter to test at the electric locking end. When unlocking the wire, whether there is more than 300 milliamps of instantaneous current passing through the unlocking wire (Yes, it indicates that the host and unlocking wire are normal, and it is estimated that the electric lock is damaged, please replace the electric lock for testing; If not, then the multiwatt-hour meter is tested at the unlocking end of the host. If so, the unlocking line is faulty, without indicating the host fault);
1.1 The tenants of the whole unit cannot open the lock, but can open the lock with password or swipe card: it is estimated that it is caused by short circuit of the main line or damage of a floor platform. First check the wiring ports of each main line. If the wiring is normal, then check the floor platform successively from the first floor platform (Check the floor platform: First disconnect the upper main line, test when the layer, if normal, regardless, if not normal, please replace the floor platform and try again, until the test is normal (such as debugging as new installation), by analogy);
Two, can not hear:
When any terminal and the host are in working state:
Any indoor phone host can not hear: the main fault is the host, check whether the host horn is connected, whether there is rust, conditions can change the horn test.
Some indoor phone host can not hear: the main problem is the indoor phone, check the indoor microphone head and line.
Can not hear the host call indoor machine: first check the indoor machine horn, see whether there is rust or poor contact, you can find a similar horn to try.
3. Don’t say:
When any terminal and the host are in working state, the host speaking terminal cannot be heard: first check whether the host microphone cable is properly connected and whether the microphone is damaged for other reasons. If possible, find a 52DB microphone head for replacement test (general extension microphone head can be common with the host);
Iv. No Video:
When any visual terminal and the host are in working state, the visual terminal cannot display the image before the host: First check whether the connection between the host camera and the host control panel is intact, and then look in detail whether the camera control panel is flooded (if there is, the camera is probably damaged). At this time, if conditions permit, take the monitor to test and connect the monitor to the video cable end of the host. If normal, it indicates that the main video cable is faulty; if not, it indicates that the host is faulty. Finally, the video signal of the camera is directly connected to the monitor. If it is normal, it indicates that the host control board is faulty. If it is not normal, it indicates that the camera is faulty.
Indoor extension problem
(For any extension problem, first check whether the extension line is connected properly, whether the power indicator is on, then disconnect the extension line again, and try again with power on)
1. Can not open the lock: (other functions are normal)
Spacing can not open the lock: first consider the key fault (installation for more than three years for most of the key fault), the extension and the host in the working state, can unlock the key touch short circuit to try the lock, normal description of the unlock key is normal; Abnormal estimate is the fault of the extension control board or the house line, and then use the 10-core sheath line for maintenance as the test line, directly connect this extension to the host line end test, normal estimate is the house line or floor platform fault, abnormal of course is the fault of the extension control board; Finally, this 10-core test cable is still used to access the floor platform for testing. If it is normal, the entry cable is faulty. If it is not normal, the port of the floor platform is changed to try again.
Two, no image:
1, no screen without image: please check the extension power supply, see whether the power supply is black and white 18V, color 12-18V;
1.1, bright screen, but the image distortion is serious, jitter, unclear, black, fuzzy: please check the extension power supply, see whether the voltage and current meet the requirements of the manual, and then check whether the line used meets the requirements;
1.2. No image on the screen: first check the video cable of the extension to see whether it is connected properly and whether there is video signal; Then replace a same type of extension test, check whether the shielding network and core short circuit;
1.3 There is an image when called, but there is no image when pressing the monitor: most of the faults are caused by the monitoring key, which can be solved by replacing it;
1.4. Other functions are normal, and there are bright spots on the display screen. Generally, the display screen is damaged.
1.5. If the display image is corrugated, consider that it is interfered by other currents or magnetic fields, check whether the video shielding wire is properly connected.
Three, can’t hear:
Can not hear, other functions are normal: first check whether the receiver is damaged, and then check whether the host voice transmitter head falls off or is damaged. In the case that both are not damaged, consider whether the receiver and the extension motherboard wiring welding points fall off, and finally consider the internal components of the motherboard.
Four: the extension does not alarm: that is, the extension with the defense area linkage alarm function does not alarm the management center!
First of all, the alarm probe is detected whether the power supply is normal, whether the work is normal, the power supply with a multimeter test, whether the work is normal by replacing the same type of alarm test; Then check whether the line between the alarm probe and the extension is smooth and whether the contact is good (this step of the wireless alarm detector), and finally replace the extension of the same model for test;
Note: General extension alarm transmission is data signal, part of the multimeter has the function of measuring data. If the multimeter has this function, it is also clear which data line of the system is, you can first use the multimeter to test the data line end of the extension, to see whether the alarm data is transmitted when the alarm, if not, it can be tested by the up method.
Five, special failure:
1.4, any extension failure, power reconnection is solved, most of the software or hardware deep fault caused by the crash, often occur such failures, it is recommended to send back to the production enterprise overhaul, so as not to bring long-term trouble;
1.5, occasionally do not open the lock, can not hear, no image, can not talk, but the number of times, with special interval, estimated to be the extension software or hardware problems caused by the crash, please send back to the production enterprise overhaul; This kind of software fault is more than the power off after the re-open disappeared fault!
Equipment problem
Building intercom system floor protector, floor decoder or video distribution amplifier and other floor intermediate equipment collectively referred to as floor platform!
(For any floor and platform problems, first check whether the wires at the end of each line are properly connected and whether the power indicator is on. Then disconnect the power line again and try again with power on) :
Floor platform must have functions: household isolation protection, video processing function, specifically, must have audio, video, data signal and power intelligent distribution and isolation protection;
1. An output terminal cannot be used normally: (other ports are normal)
Connect other normal terminal lines to the end that cannot be used normally for testing. If normal, it means that the output end is normal (that is, the line or other equipment of this end is faulty). If not, it means that the output end is indeed faulty. Only replace or repair the floor platform; Generally single output terminal or single group of output port damage, mostly caused by hardware failure, with electronic skills can be on-site maintenance, no, please send back to the supplier for maintenance.
Ii. All output terminals cannot be used normally:
At this time, the first consideration is whether the input terminal is normal. The technical measurement method will make the multimeter test, and the multimeter test whether the input terminal has signal input; If you do not know how to use a multiwattmeter, you can access an extension at the input terminal to test the function of the extension. If it is normal, it indicates that the input terminal has signal input. If it is abnormal, the input terminal line or the output terminal of the platform on the upper floor is damaged. If the input terminal is normal but not working, it is recommended to send it back to the supplier for maintenance;
Three, special fault:
Occasionally can not work, the image is unstable when working, the phone is not smooth, can not open the lock and so on, and exclude the possibility of extension, access line, the same is true when the separate test floor platform, can consider the floor platform hardware or software failure, it is recommended to send back to the supplier for maintenance;
Power supply problem
The power supply of building intercom system is one of the very important supporting equipment!
(Generally, it can be divided into two types: with battery function and without battery function. Considering various reasons, batteries are not available when Party A has no special requirements) :
The key of power supply: stability, sufficient voltage, sufficient power, to meet the needs of the system;
No power supply at the output end (check the fuse first) :
Use a multimeter to measure whether there is 220V mains input power supply:
The linear power supply of the transformer, first measure whether there is 220V mains input transformer, and then measure whether there is power supply to the control board, if there is, that the control board is damaged, it is recommended to send back to the production enterprise for overhaul;
The use of switching power supply, maintenance difficulty is higher, such as the measurement of mains input, but no output, it is recommended to send back to the supplier for maintenance;
Use more than three years of power supply, it is recommended to repair the replacement.
The output current of the power supply becomes smaller and the output voltage becomes lower:
It is recommended to replace the power supply with a new one. It is recommended to use the transformer power supply which is relatively stable and durable