1. Campus Wireless Broadcasting Overview Campus wireless broadcasting is a device that transmits broadcasts in a wireless manner. It has the characteristics of no need for pole poles, wide coverage, unlimited expansion, easy installation and maintenance, low investment, and beautiful and clear sound quality. Completely solved the problems of traditional cable broadcast wiring difficulties, complex installation, poor expansion, damage to the wall and campus environment and other issues. For the current large-scale and wide-area schools, FM broadcasting has the superiority that traditional cable broadcasting cannot match.
The advantages of using wireless FM transmission and broadcasting methods:
1. Simple installation and convenient maintenance: as long as the wireless FM broadcast connects the transmitter and the transmitting antenna with a feeder, and then the transmitting antenna stands at the highest point outdoors, the terminal uses an FM speaker, and the FM broadcast can be received when the power is on the market. Equipment maintenance is also very simple, only need to detect a certain terminal speaker or front-end equipment. It completely avoids the problem of traditional broadcast overhaul. (The overhaul of the cable broadcasting needs to be inspected all the way from the receiving terminal, the line to the front-end equipment before it can determine which part of the problem.)
2. Unlimited expansion and no bottleneck in development: As long as the wireless FM broadcast is within the range covered by the wireless FM signal, countless speakers can be used for receiving and unlimited expansion. Completely solved the problem of difficult expansion of cable broadcasting. (To increase the number of speakers in cable broadcasting, you need to increase the power amplifier and set up a line from the computer room again.)
3. Point-to-point addressable broadcasting: the front end of FM broadcasting uses coded remote control, which can perform point-to-point remote control of a certain point or a certain area of ​​the terminal.
4. Stable performance:
The FM transmitter uses a microcomputer phase-locked, and the transmission frequency does not drift.
The front stage of FM transmission adopts the most advanced dual-lock frequency subcarrier (SCA) remote control coding technology. The frequency is accurate and stable, and the remote control speaker is turned on and off reliably.
The FM receiver speakers are equipped with three firewalls (frequency, coding, address code). To enable normal broadcasting, the speakers must receive these three signals at the same time. They are indispensable.
Frequency: The FM speaker adopts the method of fixed frequency of crystal oscillator, and uses the crystal oscillator to lock the receiving frequency firmly at a point, and the frequency will never drift. It is not affected by changes in external factors such as climate and temperature.
Coding: The FM speaker needs to receive the front-end subcarrier (SCA) remote control coding signal and interpret it. In this process, it can be recognized whether the received coded signal is the corresponding coded signal set by itself, if it is turned on, otherwise it is reversed.
Address code: Each FM speaker can be set with an address code, and only after receiving its own specific address code can the speaker be turned on.
5. The sound quality is clear and beautiful: the wireless FM broadcast transmission is to send the audio signal from the FM transmitting device, and the receiving device receives and broadcasts its signal. In this process, the loss of high and low frequencies in the line is avoided, so in the FM speaker The outgoing sound is loud and loud, and the bass is thick, the whole sound line is very full, and the sound quality is beautiful and clear.
Second, the campus wireless broadcast design basis The campus wireless broadcast system follows the following national industry related standards:
"Design Standards for Intelligent Buildings" (GB / T 50314-2000)
"Engineering Design Standards for Building Intelligent Systems" (DB32 / 191-1998)
"Code for Engineering Design of Integrated Wiring System of Urban Residential Buildings" (CECS / 119-2000)
"Code for Engineering Design of Integrated Surface Line System of Buildings and Building Groups" (GB / T50311-2000)
"Code for Electrical Design of Civil Buildings" (JGJ / T16-92)
"Types of System Grounding and Safety Technical Requirements" (GB14050-93)
"General Symbols of Security Inspection and Prevention System" (GA / 74-94)
"Technical Specifications for Cable TV Broadcasting System"
National Standard GB50200-94 "Technical Specifications for Cable TV System"
"30MHz-1GHz sound and TV signal cable distribution system" GB6510-86
"Industrial Enterprise Communication Design Specification G" BJ42-1981
National standard "GB-4311 1-84 FM Radio Transmitter Calibration"
Ministry of Radio, Film and Television standard "GY15-84 FM receiver standard"
"Building Communication Integrated Wiring Standard" (YD / T926-1997)
Relevant ITU-T standards of ITU "Professional Recording Structure Standard"
3. Campus wireless broadcasting design concept 3.1 Campus wireless broadcasting design concept To build a campus wireless broadcasting system that meets the needs of modern education and teaching, to achieve the overall goal of a new generation of intelligent broadcasting that includes "multiple playback of audio sources, simple operation, human intelligence, intelligent automatic playback, and convenient expansion and maintenance" .
3.2 Campus wireless broadcasting design principles The campus wireless broadcasting scheme follows the principle of "advanced and applicable, economical and practical, safe and reliable, mature and stable, powerful, and cost-effective". It also considers important factors such as construction and maintenance, while also leaving room for future development, expansion, and transformation. The design content of this system is systematic, complete and comprehensive, and the design scheme is scientific, reasonable and practical.
3.2.1 Advancement and applicability The technical performance and quality indicators of the system should reach the international advanced level; at the same time, the installation and debugging of the system, software programming and operation should be simple, easy to master, suitable for China's national conditions and the characteristics of this project . The system integrates many advanced technologies in the world, embodies the latest development level of current computer control technology and computer network technology, and adapts to the requirements of the development of the times. At the same time, the system is a system for various management levels. Its function configuration is based on the principle of providing users with comfort, safety, convenience, and speed, and its operation should be simple and easy to learn.
3.2.2 Economy and Practicality Beijing Haiteweiye fully considers the actual needs of users and the development trend of information technology, designs and selects functions and system configuration schemes that are suitable for the site conditions and meet user requirements according to the user's site environment. , To achieve the best performance-price ratio, in order to save engineering investment, and at the same time to ensure the needs of the implementation of system functions, economical and practical.
3.2.3 Reliability and security The design of the system should have high reliability. After the system failure or accident causes interruption, it can ensure the accuracy, completeness and consistency of the data, and has the function of rapid recovery.
3.2.4 Maturity and openness Designed with existing mature products as the object, and also taking into account the current status of the surrounding information and communication environment and technological development trends, leaving room for the upgrade and expansion of broadcasting.
3.2.5 Expansion and scalability The system design takes into account the needs of future technology development and use, and has the possibility of updating, expanding and upgrading. And expand the system functions according to the actual requirements of the project in the future, and at the same time, the plan has redundancy in the design to meet the future development requirements.
3.2.6 Pursue the most optimized system equipment configuration Under the premise of satisfying the user's requirements on functions, quality, performance, price and service, pursue the most optimized system equipment configuration to minimize the system cost.
3.2.7 Reserve enough expansion capacity The control capacity of the engineering equipment is reserved to allow for the transformation of new control points in the system; the system also retains interfaces to other computers or automation systems; also try to consider future scientific Development and application of new technologies.
4. Principles of Campus Wireless Broadcasting System 4.1 Principles of Campus Wireless Broadcasting System Analog audio sources such as DVDs and microphones broadcast analog audio and are sent to the mixer for output, mixing, volume adjustment, audio modification and other composite audio signals, and digital tuner, The audio input mixer such as an intelligent broadcast control host performs audio signal switching, and then inputs it to a broadcast transmitter to transmit into the air.
The intelligent broadcast control host sends an RS-232 control signal to the broadcast transmitter. After being encoded and modulated by the encoding controller, it is transmitted with the same frequency modulation as the audio.
The wireless FM broadcast signal is transmitted in the air in the form of FM. The terminal can play through the FM speaker, or use the FM receiver to demodulate the audio signal and play it through the tweeter after power amplification. It can also be transmitted through the FM receiver controller. The FM signal is demodulated and sent to the constant voltage power amplifier to play through the lawn speaker and constant pressure speaker.
4.2 Schematic diagram of campus wireless broadcasting system
Fifth, the campus wireless broadcasting system functions to maintain order: the system has the basic functions of traditional constant pressure campus broadcasting, such as: wake-up, exercise, class, class, light-out, etc., can be set to automatically ring the timer as needed to maintain the teaching of teachers and students Order of life.
Background music: After-school meals, Saturdays, Sundays, and other leisure time, you can broadcast news broadcasts, song blessings, light music, popular songs, etc., effectively alleviating the pressure on teachers, students, life, teaching and learning, and creating an active and dynamic campus. Time and space.
Wireless transmission: Audio signals and control signals are transmitted by frequency modulation and power amplification, using the principle of electromagnetic co-generation to wirelessly transmit, saving system costs and greatly improving the stability and reliability of the system.
Addressable broadcast: The system has the addressable broadcast function, which can automatically or manually control the reception status of each FM column through the software. You can also arrange the receiving terminals randomly and play them automatically or manually through software control.
Unified broadcasting: The system can perform unified collective broadcasting according to teaching needs, and all speakers play the same program, so that the school can perform collective broadcasting, school meetings, unified audio teaching, etc.
Foreign language teaching: Recently, there is a strong demand for foreign language talents. The state will change the cultivation of students' foreign language ability from written to written, and comprehensively improve listening, so that foreign language listening teaching, training, and examinations have become new tasks undertaken by campus broadcasting. Requirements for headphones or FM radio to listen to foreign language broadcasts.
Radio Gymnastics: The system can arrange the exercises such as eye exercises, radio gymnastics, march, sports songs, etc., and set up automatic or manual play according to the needs, which can meet the requirements of students to protect their eyesight, body, hold sports games and other activities.
Emergency broadcasting: Schools are places for teaching and educating people, with a large population. The system has the function of emergency evacuation of any combination of classes for teachers and students in case of emergencies, so that the school can protect the safety of teachers and students to the greatest extent when it encounters emergencies.
Sixth, campus wireless broadcasting system features diverse programs: the system is compatible with DVD, MIDI, computer, radio, phonograph (more use in theater schools) and other program playback equipment, to meet the current format of teaching audio playback.
Auto-play: Supports playing tracks to schedule play schedule in units of weeks. The system can automatically play tracks on time according to the schedule program and automatically manage the state of the playback terminal.
Management autonomy: The system organically integrates computer control technology, single-chip technology, software programming technology, etc., fully realizing the autonomy of playback, peripherals and terminal management, saving manpower and material resources.
Wireless transmission: Adopt the frequency modulation carrier to modulate the audio and control signals, and carry the audio and control signals onto an FM high-frequency carrier, greatly improving the utilization rate of transmission resources.
Multi-listening: The system supports multiple listening methods. You can listen directly with FM speakers, or you can demodulate the signal through the FM converter and then amplify the power to listen with ceiling speakers, wall speakers, outdoor sound columns or modeling speakers.
Random expansion: There are two requirements for the receiving terminal to play the track normally, one is to have the system power supply requirements, and the other is to have the signal reception field strength requirements. Therefore, the extension terminal does not need to re-lay cables or replace the power amplifier, and it can be arbitrarily connected from the coaxial network on the basis of meeting the field strength requirements.
7. Advantages of campus wireless broadcasting system 7.1 Practicability of campus wireless broadcasting The campus wireless broadcasting system not only has many functions that traditional fixed-pressure broadcasting does not have, but also meets the requirements of modern education and teaching.
Arbitrary combination of broadcasting: the receiving terminal can be combined at will according to the need, and the timing / manual broadcasting is possible.
Unified broadcast centralized meeting: You can centralize and hold school meetings in a unified manner, and you can also broadcast content at the sports meeting.
Facilitate education and teaching management: not only complete the maintenance of teaching order, but also integrate foreign language teaching.
Compatible with a variety of audio sources to play: can play FM, CD, tape, WAV and other formats of audio.
7.2 Stability of campus wireless broadcasting As a transmission method of broadcasting, campus wireless broadcasting has been applied in China for decades, and the technology has been quite mature. Now it is applied to campus broadcasting, its stability and reliability There is no doubt that Hitewell Wireless Intelligent FM Broadcast is mainly reflected in the following two aspects:
Audio signal modulation and demodulation: The audio signal modulator uses PLL phase-locked loop technology to lock the phase of the modulation frequency to avoid the occurrence of drift in the modulation frequency; the receiver uses a technology of crystal oscillation stabilization frequency to stabilize the reception frequency at the required In frequency, the receiving frequency is accurate, stable and reliable.
Control signal modulation and transmission: the control signal of wireless intelligent FM broadcasting is modulated on the SCA idle subcarrier of the audio frequency to ensure that it is not interfered with to the greatest extent, and stable and reliable transmission.
7.3 Campus Wireless Broadcasting Economics The campus wireless broadcasting system of Haite Weiye has effectively solved many new demands for campus broadcasting in the current education and teaching. On the basis of meeting its various functional requirements and practical requirements, it also has a certain perspective. It has the economy that other systems do not have.
Wiring angle: Intelligent broadcast and control signal share the same frequency, the two are combined into one in transmission, saving wireless frequency resources.
Construction angle: To build the broadcasting system, there is no need to lay signal cables, just lay the power cord nearby, the construction difficulty is greatly reduced, and the construction period can be shortened by two thirds.
Management perspective: The system achieves autonomy in broadcasting, management, and control, so that the system does not have to be responsible for specific people, and it can be played at a fixed point. This not only saves the human resources required for system operation, but also greatly improves the safety, punctuality, and reliability of broadcasting. Sex.
Maintenance perspective: The intelligent broadcast and closed-circuit television systems use wireless transmission. No maintenance is required on the transmission side, only the system equipment can be maintained.
Expansion angle: The system expands the terminal receiving equipment without replacing the power amplifier or re-laying the cable, and adding the terminal directly within the signal permission range.
8. Campus wireless broadcasting solution design 8.1 Campus wireless broadcasting audio source design is mainly composed of audio sources (analog audio sources from the digital audio source output from the playback host, radio head, microphone, etc.), mixing console (audio signal switching equipment), intelligent broadcast host (send Digital audio source and control signal), broadcast transmitter (broadcast and control modulation transmission equipment) and so on.
8.2 Campus wireless broadcast control design By combining the code control board and the computer, the entire broadcast system is intelligently and automatically controlled. With coded remote control, you can freely control the broadcast of a certain point or area on the interface, or you can manually control it.
8.3 Campus wireless broadcast transmission design It consists of a transmitting antenna and a feeder. The audio and control signals are first modulated onto the FM FM carrier and SCA subcarrier, and then transmitted into the air.
8.4 Campus wireless broadcast reception design The classroom, dormitory and office building corridors use crystal frequency stabilization processing indoor FM speakers for listening, outdoor use FM sound column for listening, and the playground uses "FM receiving controller + constant voltage amplifier + constant pressure sound column" Listen.
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