Shanhaiguan city, with a circumference of about 4 kilometers, is connected to the Great Wall, with the city as guan. The city is 14 meters high and 7 meters thick. There are four main gates and various defense buildings.

Scenic area covers an area of 0.1 square kilometers, including the first pass "day" embrasured watchtower, jingbian-yanshuiguang pipeline building, barracks, Lv floor, red lotus pavilion in the park, barbican, a square line meter and 1350 plains of Ming dynasty the Great Wall and other landscape. The scenic spot covers the landmark building of the shanhaiguan - "the first archery building in the sky". It is the most complete military defense system of the Great Wall to date. "The first archery building in the sky", also known as "the east gate of the town", is the east gate of shanhaiguan city. According to the county records of linyu county, it was repaired many times during the Ming and qing dynasties, and it was repaired many times after liberation. The building area of the city is 198 square meters. Its buildings are the top of the eaves and the four corners are decorated with different types of ridges, with 68 holes in the north, east and south. Above the archery, the most striking is the "first pass of the world" giant plaque, inside and outside the three plaques, the first floor hanging from the original plaque.

On March 4, 1961, the Great Wall - shanhaiguan was published by the state council as the first batch of national key cultural relics protection units.

Project in accordance with the specific requirements of scenic area to the radio, in line with scientific, advanced, practical, safe, economic and other principles, it is recommended to use and adapt to the modern information society the high-tech, high-quality products, make the scenic area radio and really become good staff tools, more major is not just production, living and entertainment, the role of the emergency response message in an emergency, but also other tools cannot replace.

Wireless FM radio is to use high frequency waves for transmission cover, without digging ditches poling and wiring, as long as there is power supply can install the radio, anywhere can listen to the radio, digging out the vertical rod and wire of engineering investment, economic and does not destroy the existing buildings, radio waves transmit radio signals, line to line loss, without any sound high reducibility, CD of the same sound quality can be obtained, on the use and maintenance of the complex circuit is linked together, more convenient and simple, is an environmental and economic relief project.

Scenic spot broadcast as a kind of information transmission media, it should be the first comprehensive control ability, the use of wireless FM radio is covered by high frequency waves, not bound by environments and places, visitors can enjoy the beautiful background music, can also according to different audience addressable broadcasting anytime and anywhere, have very strong control ability; Therefore, the information of the first session can be transmitted to the audience of different time, content and location.

As a carrier of information transmission, scenic spot broadcasting has a wide range of practical value, which can play emergency emergency notification and disaster prevention and relief. From the entertainment aspect: can play the beautiful and healthy music track, create a relaxed travel environment, beautify the spirit, beautify the life and so on.

Scenic spot broadcast a total of four sets of launch system, can launch four sets of programs at the same time, greatly enriched the campus broadcast content, applied to the real work has been very perfect, powerful.

A. The system plan is described

With the progress of society and the development of science and technology, digital information technology has been very mature. The application to the real work has been perfect and powerful.

1. System overview

(1) investment province: wireless transmission system shall be adopted to realize the demand for broadcasting in the same time without rewiring.

(2) stable performance: due to the use of FM-SCA FM modulation technology, it is not subject to external electromagnetic interference and stable performance.

(3) functional: controlled by computer software and hardware control, which can realize timing play background music, point-to-point addressable broadcasting: FM radio the front end of the use of remote control code, can be a point or a zone of terminal point to point the remote control. Radio stations with addressable features can be used to pick up the FM receiving device at any point (area) at the broadcast center for point-to-point broadcasts and announcements.

System of FM reception facilities set up four firewall (frequency, subcarrier, code and address code), sound box to open the normal broadcast at the same time must be received the four kinds of signals, be short of one cannot, so resolutely put an end to boot.

Frequency: the frequency modulation receiving device USES PLL to automatically correct digital lock phase and modern communication cell phone mode, with the receiving frequency firmly locked at one point, the frequency will not drift. It is also not subject to changes in the external factors such as climate and temperature.

Coding: the FM receiving device needs to receive a front-end subcarrier (SCA) remote code signal and translate this. In this process, it can be recognized that the encoded signal received is the coded signal corresponding to its own, and it is opened, otherwise it is not.

Address code: every FM receiving device can set an address code, only to receive the specific address code belonging to it, can be opened.

Sound quality: the traditional cable broadcast is transmitted by power, not only the power loss is large, but the high audio loss is large, so the sound is more stuffy, not clear. Wireless FM radio transmission is high frequency signal, there is no problem of power loss. Therefore, in the same loudness of the speaker, compared with the cable broadcast, the power of the equipment can be over 20%. Without high frequency loss, sound quality and clarity.

Two. Based on the digital FM broadcasting system,

In accordance with the relevant documents, standards and regulations of the state, mainly includes: the bureau of standard "FM receiver GY15-84 standard" the professional recorded structure standard "technical specification for cable television broadcasting system gb GB50200-94 technical specification for the cable television systems engineering of the 30 MHZ - 1 GHZ voice and television signal cable distribution system" GB6510-86. Communication design specification for industrial enterprises gbj42-1981. Specification for electrical design of civil buildings GBJ/t16-1992. International ITU - T standards. Construction, communication related industry standards.

3. Design principles for system design,

In line with the principle of "advanced, scientific, stable and economical".

Advanced frequency: FM transmitter adopts the most advanced FM-SCA FM demodulation technology, while adopting the latest microcomputer PLL lock phase technology. Ensure that the sound quality is clear and graceful, the switch machine is accurate and reliable.

Scientific and reliable scientific: system design, the system will ensure the independence of the radio frequency, will not happen with other radio waves interference phenomenon, remote speaker receive flexible adjustable frequency point, at the same time ensure that speakers interference phenomenon will not occur. In addition, the system is guaranteed to be maintainable and fully expandable.

Stability: the system USES wireless FM radio, save a lot of wiring system, so also eliminates as radio system is most likely to happen in broadcast system which caused by the problem of line fault line fault phenomenon; At the same time, the equipment adopts fm-sca subcarrier code control technology, which can not open the speaker box, which greatly improves the stability and reliability of the system.

Economy: this system maintenance is convenient, simple structure, concise layout, no air lines, underground buried lines, visible economy of broadcasting system, saves in the construction of a large number of transmission wire and track laying cost, in use process can save a lot of line maintenance work, save a lot of maintenance costs