Comprehensive analysis of access control system network cabling

Foreword

The access control system is a subsystem of the access management system. Usually, it uses the technology of swiping cards, passwords, or human biometrics to manage the entrances and exits of people or vehicles under the control of the management software, so that people and cars that have obtained the approval can enter and leave freely. And those who should not go in and out are prohibited and interfered. Since the access control system can quickly identify the identity of a person or a car, the access control system has rapidly evolved from various possible developments over more than a decade. Like the use of the access control system, it has entered the residence, entered the office building office, parking, subway and It can be used at the entrance of the hotel to confirm the identity of the visitor. It can also be said that in many premises access systems that need to check the identity of people and vehicles have become indispensable configuration items. Therefore, in engineering projects, access control is a unique project implementation technology for security workers, and access control technology projects have a larger proportion of networked communication technologies. We will explore these access networks in this issue. Communication technology is actually applied.

What are the access control system application modes?

Before discussing the construction and application technologies of access control networks, we need to have some understanding and understanding of the mode of access control to the main brother of the access control network in accordance with the different modes of access control, so as to talk about the technology of networking and communication. It will be more architectural in concept, and it will also be able to grasp the key points of construction methods in construction.

All equipment and accessories in the access control system should also comply with China or international relevant cyber security standards while operating safely and reliably. They can also work effectively in non-ideal environments. Strong real-time monitoring and linkage capabilities fully guarantee the safety of the user environment, the technology of the access control system continues to evolve, and user needs are changing. Therefore, the design and implementation of the access control system should take into account the practical feasibility of future expansion. Need, that is: can be flexible additions and deletions or updates of various subsystems to meet the needs of different periods, to maintain a long lead and become a code for intelligent buildings. When the system is designed, the functions that need to be implemented are reasonably configured, and this configuration can be changed. Even after the project is completed, this configuration change is possible and convenient. The system software conforms to different history according to the developer. The needs of the period market will be upgraded and improved accordingly, and free software upgrades will be provided for the corresponding application customers free of charge. At the same time, it can be expanded into attendance systems, meeting attendance systems, patrol management systems, and meal management systems and other card projects. The structure and configuration of the access control system can be roughly divided into the following four ways according to the function management structure model to facilitate the construction of network engineering applications.

Mode 1: One-way induction (card reader + controller + exit button + electric lock)

The user presents an authorized proximity card outside the door. After the card reader recognizes the legal identity, the controller drives the electric lock to release and records the door entry time. Press the door open button to open the electric lock and go out directly. Applicable to a general security level environment, can effectively prevent illegal entry of outsiders. Is the most commonly used management model.

Mode 2: two-way induction (card reader + controller + card reader + electric lock)

The user presents an authorized proximity card outside the door. After the card reader recognizes the identity, the controller drives the electric lock to release and records the door entry time. When the user leaves the controlled room, an authorized proximity card must also be presented in the door. After the card reader recognizes the identity, the controller drives the electric lock to release and records the exit time. Applicable to a higher level of security, not only can effectively prevent illegal entry of outsiders, but also can query the last person and time left, to facilitate the implementation of the responsibility to provide evidence for a specific period (such as when stolen).

Mode 3: Card + Password (card reader + controller + exit button + electric lock)

After you finish the card, you must enter the correct password to open the door. The password is a personalized password, that is, one person and one password. The advantage of this is that, for more secure applications, even if the card is picked up and cannot be accessed, the correct password must be entered. And you can easily set the mode, for example, for the same door, some people must be allowed to enter the card + password, some people can swipe, you can enter without a password, a specific person can enter the password is released.

Mode 4: Card + password + time period (independent access control host + exit button + electric lock)

No external card reader is required for this mode, and the reader is integrated with the controller. The door opening mode is divided into: 1 card + time period 2 password + time period 3 card + password + time period.

From the above four types of structures, we can clearly understand whether or not the model is based on the North. The structure of the North is roughly based on these parts. The connection and security of these parts are linked to the security of the entire network. Of course, there are many users and vendors in the past who stated that access control is nothing more than a sterile closed circuit or network environment. It is certainly understandable in the past. However, at this stage in the current stage, everything is infallible. To stress the remote control and IP network today, one of the most common words in Netcom's community is that "as long as the system goes online, there is no absolute security at all." It can be seen that network application security is also inaccessible in the access control system. In part, let's take a look at the connection between wireless transmission structure and network application security in access control engineering network communication.

Access Control System Communication Engineering Principles and Network Routing Principles

The communication system of the access control system is basically similar to that of other automatic control systems or intelligent building systems. Its operation can be divided into sensing, management, and execution. It is only relatively compact and relatively simple.

Sensing: Card readers, password keyboards, various biometrics, exit buttons, and lock status sensors all belong to the sensor device. Their task is to accept commands and upload the signal or upload it after verification (biometric identifier).

Management: The controller and management software are responsible for the management function of the access control system. After receiving the information from the sensors, they determine whether to open the door based on time, card number, and other information. If the door is opened, a door opening command is issued to the electric lock. . When the lock status sensor is received, it starts timing, and it will alarm when it times out.

Execution: When the electric lock receives a command to open or close the door (power supply or power off), it executes the command to adjust the working status to match the command. The lock status sensor in the electric lock plays a role of feedback and supervision. Some controllers can use relays (or other contact switches, commonly known as hard contacts) to output control signals to control linked cameras and lights.

Access Control System Transmission Lines

Based on the above work principles, there are the following types of transmission lines in the access control system:

Power line: The power supply of the access control system is mostly from the UPS of the equipment room so as to avoid the door opening malfunction caused by sudden power failure at the site. The power line is usually delivered at 220V AC to reduce the voltage drop on the power line. Beside the controller, equipped with a power supply, AC 220V power into DC 12V power supply, respectively, to supply the controller and the electric lock. Most of the electric locks used in access control systems are 12V DC power supplies. At the instant of the opening of the electric lock, due to the action of the electric coil (electromagnetic coil) in the middle of the electric lock, a strong current will be generated on the power line, which easily causes power supply fluctuations, and this power supply fluctuation is extremely stable for the controller. Unfavorable, so in the access control system with high reliability requirements, the controller and the electric lock respectively use different power supply modules, that is, when 220V AC power is supplied to the controller, after using two 12V DC power supply modules to each rectify/regulate the power supply module, Supply electric locks and controllers separately. The selection of various power cords is basically based on the electrician's manual, using the standard power cord.

Controller signal line: The controller has a group signal line, which is connected to the card reader, the lock status sensor in the electric lock and the exit button. This route signal line can be replaced with a twisted pair cable in the composite line. In order to avoid electromagnetic interference in the space, the reader signal line is shielded, and the other two signal lines can be shielded or non-shielded.

Remote network signal line: There is a signal line from the controller to the management computer. Most of the transmission protocol is RS485. When the distance is near, it may be RS232 (to reduce a RS232/RS485 converter). When the transmission rate is required to be fast, the TCP/IP protocol is used to transmit using Ethernet. Twisted pair can be used for this type of protocol. However, in the case of RS485 or RS232 transmission, the shielded cable is basically required in the product manual of the access controller. In order to avoid electromagnetic interference, this signal line applies shielded twisted pair. When the controller needs to directly control the hard disk recorder using the output hard contact (simultaneous recording when opening the door when swiping the card), the control cable (2 cores) should be shielded to avoid electromagnetic interference caused by the hard disk recorder input signal amplitude is small. Causes false triggering. However, if you are using a hard contact to directly transmit the lamp power, you should use the power cord. According to the above analysis, when the transmission power supply (power supply for the electric lock, controller, and lighting lamp) is applied, the cross-sectional area can be calculated based on the voltage drop and heat generated by the current, and can also be found in the electrician's manual. When transmitting sensor signals and control signals, shielded or unshielded cables should be selected according to the reader and controller installation manuals. With more and more gates controlled by access control system locks, the requirements for the system's network transmission speed and line security are getting higher and higher, and the construction of the access control system is also more complicated than the construction of the integrated line system. The use of a network twisted pair cable as the transmission line of the access control system has become the main choice for the cable of the access control system. According to the analysis of various access control cables, network twisted pairs can be used for the signal lines and control lines between the card reader, controller, and management computer.

In the case of both the access control system and the integrated line, the network twisted pairs with distances shorter than 20 meters often do not meet the utilization value in the integrated line project and become an engineering waste line. However, these short-rejection wire rods are often used for the split-mounted controllers as the exit button signal line, reader signal line, and lock status signal line. For the remote network signal line using the TCP/IP protocol, twisted-pair transmission is indispensable, and it is possible to use the star system of the integrated line system to realize signal transmission. RS485 cable and RS232 cable can also use twisted pair cable. According to the installation rules of the access controller, these devices should be shielded twisted pair to avoid malfunction caused by electromagnetic interference.

Network application integrated line in the access control system

When using the integrated line system as the transmission line of the access control, the following factors should be noted: The wiring method should be completely in accordance with the wiring rules of various access control devices, and retain the detailed wiring diagram to avoid the pain when determining the line during maintenance. Shielded twisted pair shields should be grounded according to the reader and controller installation manual.

If you use a network-shielded twisted pair cable for TCP/IP, you can completely use the shield termination rules for shielded-line systems. When using the TCP/IP protocol, it is best not to share network switches with other smart systems (including software systems such as office automation systems). That is, a separate network switch is provided for the access control system so as to avoid unexpected transmission accidents due to the protocol. When using the network TCP/IP protocol, the management computer of the access control system can be considered as a server in the access control network, and is connected to the distribution frame using twisted pair or optical cable. The integrated line system can be used for access control systems. This has been confirmed by the suppliers and installers of the access control system. It is only in the project that the cost, construction and performance should be fully evaluated in order to achieve the best results.

The access control system transmits wireless network security applications

Since the birth of the wireless access control products, the continuous evolution of technology has led to the adoption of FSK, GPRS, Bluetooth, ZigBee, and other transmission methods. With the rise of the Internet of Things technology, Internet of Things access control products have been subject to a general barrier within the security industry. As described in the previous two paragraphs; traditional access control solutions are networked and controlled by cables that are routed to each door point. However, as the project started one by one, more and more industry peers and customers began to realize that there are many cables in the wired network system itself and installation and construction are in trouble. For example, conventional locks (electric locks, magnetic locks) are not aesthetically pleasing, have poor reliability, cannot be used after a power failure, and are maintenance-inconvenient. Therefore, many powerful access control companies are exploring novel requirements that not only meet the demanding requirements of security systems for access control, but also avoid the many defects of the current wired networked access control systems. Wireless access control has gradually begun to be recognized and applied by people.

People choose wireless access control products, the main purpose is to reduce the wiring complexity. Because the access control has centralized management requirements, each door point must communicate with the center. If wireless communication is selected between the access point and the center, too many access points and the center's communication lines can be saved. This is inconvenient in some wirings. The occasion is very attractive. The first generation of wireless access control was born under the above technical background. Such devices mainly communicate through the free frequency bands specified by countries such as RF315M and RF433M. The communication technology adopted is also relatively simple. Generally, basic wireless systems such as FSK or FMK are used. The modulation method is fixed at a fixed frequency. When multiple devices work together, they will interfere with each other, and the communication speed is also low, generally between 300bps and 1200bps. Because the technical means are relatively monotonous, the problems of poor communication stability and reliability prevail in use. Such products have gradually faded out of the market. The concept of wireless access control for mobile phones was proposed along with the development of mobile phone technology. Because the first generation of wireless access control could not meet the needs of some specific locations and industries in terms of communication and transmission distance, some of the manufacturers of access control tied mobile phone modules and door controllers. Together, control signals are transmitted wirelessly via SMS or GPRS through Unicom's mobile network to achieve the purpose of long-distance signal transmission. However, mobile phone wireless access control is due to equipment costs, mobile phone rental fees and other related fees collected, the use of high cost, while the signal through the GSM network transmission delay is large, the performance is not ideal (communication rate can only reach 20-40kbps, and speed Unstable), making mobile phone wireless access control products currently only limited to occasions with certain needs, the use of the industry.

At the same time, the wireless Internet of Things (IoT) access control system using the wireless Internet of Things technology has also been subject to widespread market acceptance. It is predicted that the Internet of Things will become the same technology that changes people's lives as the Internet, and IoT technology will be applied to wireless. Access control will undoubtedly occupy the highland of wireless access control technology in the future, and the market prospects will be enormous. Unlike the wireless access control that uses Bluetooth and ZigBee technology for wireless signal transmission, the Internet of Things (IoT) access control focuses more on the intelligent perception of access control and low power consumption. Although Bluetooth and ZigBee are low-power short-range wireless transmission technologies, they are used in The battery-powered IoT access control system is still too power-consuming.

Wireless Internet of Things Access Control System: no wiring, reliable, energy-saving

The access control system was accompanied by a large amount of wiring from the first day of its birth. A complete access control system consists of eight modules: card reader, controller, electric lock, exit switch, door magnet, power supply and management center. All modules need to be online. At the same time, the front and back of the door frame and the top and the top of the door must be perforated to install the equipment. Therefore, the construction is cumbersome and very intuitive. The wireless IoT access control simplifies the door point device to the extreme: a battery-powered lock. In addition to opening the door to lock the door above, there is no need to install any auxiliary equipment around the door. The entire system is concise and clear, significantly shortening the construction period, and can also greatly reduce the cost of post-maintenance.

Frequency hopping and encryption are another core of wireless access control. One big difference between wireless and wired is that the wireless signal is transmitted in the air, so it is easily disturbed by the outside world, and it is also easily captured by the outside world. Therefore, security and reliability can be said to be the lifeline of wireless access control products. The security and reliability of wireless IoT access control systems are mainly reflected in the following two aspects: the security of wireless data communications and the stability of the transmitted data. Wireless IoT access control system uses intelligent frequency hopping technology to ensure that signals can quickly avoid interference. At the same time, dynamic keys and AES encryption algorithms are used in the communication process. Even if it is the same instruction, the communication packets transmitted in the air are different each time. , so listeners can not intercept. However, for wireless technology, data packet encryption technology can be understood and accepted by everyone, and the wireless anti-jamming capability is a topic that can not be avoided. In response to this problem, the wireless IoT access control specifically designed the offline work mode. This is a work mode that ensures that the door can be normally opened after the wireless interference is disabled or the center system is down. Take the wireless door lock as an example. When the communication fails, it equates to an unconnected hotel lock, and the door can still be opened and closed (the same as the opening permission when the internet is connected). The user does not feel the difference between offline and online. The only difference is that the card data is downloaded offline. It is not transmitted to the center in real time, but it is temporarily locked and automatically uploaded after the communication is restored. The wireless Internet of Things is an ultra-low-power product, which will make battery-operated life longer; only battery-powered, there is the possibility of complete wireless. The communication speed of the wireless IoT access control system reaches 2Mbps. The faster communication speed means that the shorter the signal is transmitted in the air, the less power is consumed. At the same time, the lock used in the wireless IoT access control system is only to perform the opening and closing of the door. It consumes electricity only when it is in motion. Wireless IoT access control systems can directly replace existing wired or non-networked access control systems. For office building systems, the application of wireless IoT access control can significantly reduce the construction workload and reduce the cost of use; for hotel systems, it can enhance the intelligent level of access control. However, for any new things, there are inevitably some doubts in the market. How to dispel users' concerns about the stability, reliability, and security of wireless systems is the biggest problem in market promotion. We believe that with the promotion of the Internet of Things technology and the development of wireless Internet of Things (IoT) access control cases, the wireless Internet of Things (IoT) access control system will surely become more and more popular with users.

in conclusion

In essence, the vast industries of security, communications, and IT are the process of processing information on access control systems, and they are all moving toward the development of the Internet platform. Then this technology will definitely be a ban on Internet access. The core of security technology for network communications. The security threats to Internet access in access control are few, but they generally come from the backdoor or Trojan Horse (Trapdoor/Trojan Horse): Unauthorized programs can be screened by legitimate programs and disguised as a process of access control authorization. , To run a program, or to snoop (Sniffer): The user's identification data or other confidential information, in the process of network transmission, is obtained by illegal third-party learners or access to important access control information and the last type of masquerade (Masquerade): The attacker pretends to be a legitimate user and gains access to use. However, these are the inevitable risks in network access control. It is the safest choice to make the best choice in the construction and application of access control network projects.