by Michael Kappel

Article by jekky

In recent years, the world of fire fighting and rescue the situation gradually become socialized, global, complex and intelligent and so on, Fire The particularity of relief on the scene to protect fire commanders and command communication links between objects put forward new and higher requirements. U.S. in the “9? 11″ rescue operation, due to communication limitations result in fire stations and police stations as well as other departments can not coordinate command and control, not the exchange of relevant information, leading into the World Trade Center tower fire commanders can not receive Accident Comprehensive information about the regional situation report, not sure the tower disaster situation and level of development. As the device frequency differences, can not receive the police helicopter circled over the issue of the tower Collapse Warning that a partial collapse, leading to the 343 firefighters killed on duty. A large number of ambulance vehicles were repeatedly sent confusion due to communication the World Trade Center, adding to the communication, traffic jam. “9? 11″ on its rescue communications systems of major disaster events in the face of serious problems, but also reflects the modern fire rescue communications to protect the special nature. One scene, there are many reasons for poor fire fighting and rescue communications field commanders to obtain accurate, reliable and timely information for the entire fire fighting and rescue operations played a key role in the success. Communications and liaison to the rapid, accurate and uninterrupted. The cross-regional, super depth and breadth of such a fire scene, super-communication protection has become increasingly prominent. The existence of such a scene, a lot of issues I think that poor communication has the following main reasons: First, external radio interference. External radio interference can be classified according to their characteristics of impulse noise and interference fluctuations. In fire and rescue process, the pulse intensity and interference with the greatest impact, but the duration is short, mainly from various Electric Equipment generates pulses of electricity. Such as motor vehicles and driving at the start of the ignition so. Second, intermodulation interference. Intermodulation interference is mainly multiple signals generated by nonlinear devices added to a large number of intermodulation products generated. When two or more signals simultaneously added to the non-linear device, because of the characteristics of the device to produce a variety of mixing the product of these signals, if some mixing into the product of the pass band walkie-talkie and a certain intensity . Would interfere with the radio. Third, adjacent channel interference and interference with the channel. Adjacent channel interference refers to the adjacent or between adjacent channel interference. The use of mobile base stations for emergency communications, the mobile station launched sideband modulation sideband noise expansion and radiation, will be on the weak signal is received the base station receiver adjacent channel interference; same channel interference refers to the base with the same frequency the interference between the units. These phenomena will cause the scene, the received radio signal distortion or signal to noise ratio is too low, so that call quality has declined. Fourth, the shielding effect. Shielding effect of electromagnetic waves in the propagation of electromagnetic waves has a great impact. Radio wave propagation is based on the form of electromagnetic energy campaign, radio propagation of electromagnetic waves during the process, in the event of reinforced concrete and other metal objects will produce alternating reinforced within the induced current, alternating current will be induced the formation of alternating magnetic field, thus affecting the transmission of radio waves, causing radio communication can not be normal. Fifth, the signal attenuation. The main receiver Technology Indicators, including sensitivity and selectivity. If the transmission power is small, or radio in the dissemination process of the obstacles encountered over the wavelength range, such as mountains, trees, large buildings, vehicles and other objects can not be diffracted waves, the receiver receives the signal will change very weak. 2 solve the scene, communication problems 1, signal interference resolution. Fire communication signal interference is the most common interference. Include intermodulation interference, adjacent channel interference and interference with the channel. Intermodulation interference signal added to the number of non-linear devices are formed. Therefore, the interference signal, it must meet specific frequency relationship and a certain rate, the order form Intermodulation interference. Therefore, the Commission can be strengthened through local radio radio allocation of space management, strengthen cooperation, strict law enforcement, prevent the formation of intermodulation frequencies. For the same channel interference, mainly increase the scope of the standard management of 350m band, to prevent or reduce some of the same frequency range occurs. 2, using wired communications, simple communication aids.

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I am an expert from Frbiz Site, usually analyzes all kind of industries situation, such as double rocker switches , distinctive ring switch.

Jonathan Boulet is the newest player in the Modular clubhouse, a precociously inspired 21 year old skate rat from Sydney’s Northwest. A Community Service Announcement is the righteously smashing single from the Jonathan Boulet album, already a repeat performer at alternative and community radio. An inspired call to arms for 21st century dreamers, A Community Service Announcement’s unbridled joy is matched only by the riotous natural and digital destruction in it’s accompanying video, directed by New Zealand duo Special Problems. Pre Order album: www.jbhifionline.com.au www.modularpeopleshop.com