The college entrance examination is coming soon, Jingzhun GPS Beidou satellite timing system (Master clock) helps standardize the examination
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【Abstract】The clock system is an important precise timing system in the campus network. With the popularization of the network, many campuses have built their own campus private network, and the number of network devices and servers used is also increasing. These devices have their own clocks. , and is adjustable. However, there is no guarantee that the clocks of all devices and hosts in the network are synchronized, because these clocks will have errors of several seconds or even several minutes every day. After long-term operation, the time difference will become larger and larger. This deviation has little impact on a single machine, but it may cause unexpected problems in applications in a network environment.
1. Overview
With the popularization of the network, many campuses have built their own private campus network, and more and more network devices and servers are used. These devices have their own clocks and can be adjusted. However, there is no guarantee that the clocks of all devices and hosts in the network are synchronized, because these clocks will have errors of several seconds or even several minutes every day. After long-term operation, the time difference will become larger and larger. This deviation has little impact on a single machine, but it may cause unexpected problems in applications in a network environment. For example, in a distributed computing environment, due to the inconsistency of the clocks of each host, the recording time of the same operation on different hosts will be inconsistent, which will cause the service to fail to proceed normally. With the continuous development of various network applications, the requirements for the clock are getting higher and higher, otherwise many problems will be caused.
The campus is composed of classrooms, offices, libraries and other places. The clock information in each place is inconsistent, and the work of teachers and students cannot be coordinated to achieve the highest efficiency. It may have little impact on normal work, but because of the clock inconsistency in key exams, students cannot pass the test. If the level is not high, the teaching performance of teachers cannot be evaluated, which has a great impact.
2. System equipment composition
The network clock system consists of satellite signal receiving antenna, NTP satellite clock server (NTP network master clock), network switch, NTP network slave clock, transmission channel (network cable), management software, etc. The system structure is shown in Figure 1.
2.1 Satellite signal receiving antenna
The satellite signal receiving antenna consists of a satellite mushroom head and an antenna of appropriate length, which can provide satellite real-time synchronization signals to the satellite clock server (network master clock).
2.2 Satellite clock server (network master clock)
The satellite network master clock in the clock system is a dual-machine backup device, one of which is the main source of the system time signal, and the other is the equipment backup of the entire clock system, in case of emergency failure. The satellite master clock LCD display can display year, month, day, hour, minute, second time information and the current number of GPS Beidou satellites. The clock system consists of two high-stable satellite network master clocks, satellite receiving antennas, antenna brackets, client software, etc.; the
multi-channel network port of the satellite network master clock can be sent to the classroom and office digital NTP network slave clocks, and can also be sent to the campus at the same time The server monitoring hosts of broadcasting system, security system, smart classroom system, smart library system, fire alarm system, campus card system, campus information management system and other subsystems provide standard time signals.
2.3 NTP network slave clock
The network slave clock (that is, the time synchronization display screen) is installed in classrooms or offices, libraries, corridors, security monitoring rooms and other important places that need to display the time.
The network slave clock is digital. It can display hour, minute, hour, minute, second, year, month, day, week, hour, minute, and second, and can be ordered according to the actual needs of the site. The network slave clock automatically sends a time synchronization signal request, and the satellite clock server (network master clock) automatically responds and realizes the time after receiving the slave clock request. Synchronous work.
The network sub-clock adopts frosted PC panel, which is anti-glare and not dazzling; the ultra-thin metal shell design is electrostatically sprayed; the Chinese characters of year, month, day and week are self-illuminating and integrated with the numbers.
2.4 Transmission channel
The transmission channel between the master clock of the satellite network and the slave clock of the NTP network can use Category 5 or Category 6 network cables to manage the communication lines, and all devices use standard RJ45 network ports.
2.5 Management software
The management software can be installed on a high-performance computer to monitor the running status of the clock system in real time through the network transmission channel.
The management software can check the operation status of any network sub-clock in the clock system, and perform necessary operations on any network sub-clock in the clock system (calibration, stop, reset, time tracking, time setting, etc.). When the system fails, it can accurately record the time and location of the failure, and can conveniently view and provide accurate data for maintenance.
3. System functions
The basic functions of the clock system are as follows:
3.1 The synchronous proofreading
system continuously receives the time code and related codes sent by GPS/Beidou satellites through the satellite signal receiving antenna, and analyzes the received data to judge whether the data is true and reliable . If the data is reliable, it will be adopted by the master clock of the satellite network. If the data is unreliable, it will be discarded and continue to receive next time.
The network slave clock is an independent display unit, which can run independently from the satellite network master clock, and at the same time, it can actively request the standard time information of the satellite network master clock, and the network master clock can check it in real time. In order to ensure that the received information is true and reliable, the network master clock strictly analyzes and judges the received request information to eliminate interference information.
3.2 Time Display and Adjustment
The time of the digital network slave clock adopts the optional mode of "hour, minute; hour, minute, second; year, month, day and week". The information is sent out to adjust the time of the sub-clock.
3.3 Provide time signals for other systems.
The satellite network master clock is equipped with 4 NTP network interfaces (RJ45), and each network interface has an independent MAC address. They are physically isolated from each other and do not affect each other. They can always be ready for the campus network and other subsystems. Provides a time synchronization signal. The main systems include: broadcasting system, security system, smart classroom system, smart library system, fire alarm system, campus card system, campus information management system, campus computer room server, etc.
3.4 System monitoring function
The computer system for managing and monitoring the clock system is set up in the control center, which has a self-diagnostic function, and can perform fault management, performance management, configuration management, safety management, etc.
The management computer in the center can detect the operation status information of the sub-clock equipment, and display the detected fault status, can reflect the status of each module in the system in real time and in detail, and can perform point-to-point control (reset) of the entire system clock , stop, proofreading, chasing time, etc.).
When the system fails, it can send out sound and light alarms, indicate the location of the fault, and transmit the fault alarm synchronously, provide it to the staff in the duty room, and perform fault recording and printing.
3.5 System scalability
When the system expands, the network master clock in the center can be expanded in real time through expansion equipment to facilitate the addition of network slave clocks at each site.
3.6 The distributed control
system adopts the distributed control function, that is, a distributed system. The central network master clock and the network slave clock are connected to each other through five types and six types of shielded network cables. They are relatively independent in the entire system, and any part of the failure will not affect the system. operation of the entire system.
4. System configuration principles
The campus is composed of classrooms, offices, libraries, weak current security control rooms and other places.
The installation method and size of the clock can be determined according to the installation location. For the size and display content of the satellite network master clock and each slave clock, and the installation location, refer to the suggested configuration table:
5. System summary
The clock system is not only convenient for enterprises and institutions to keep accurate time, but also can greatly improve their work efficiency. The improvement of efficiency means the improvement of social public services, and the strong attention of enterprises and institutions to time is precisely their service and Efficiency-conscious testimony.
With the establishment of big data in various units, the number of network equipment and servers continues to increase. When network administrators check the logs of many network devices, they often find that the time is different. Even if the time is manually set, there will be time errors caused by factors such as time zone or daylight saving time; after restarting some Layer 2 switches, the clock will return to the initial value. The time needs to be reset. For core network devices and important application servers, they sometimes need to work together, so the unified accuracy and reliability of time is particularly important.
At the same time, the clock system has industry-leading environmental protection performance, leading the urban green office trend. With the continuous acceleration of the pace of modern life and the popularization of the Internet, the demand for time accuracy is getting higher and higher, especially in the current airports, railways (subway and railway stations), hospitals, schools, government agencies, enterprises and institutions. Units, etc. just cater to their needs and solve real problems for them.