Yesterday, Ms. Du, who lived in Jimo, called the hotline, saying that her family lived at school and had a cell phone signal shield that had been used in school exams yesterday to affect her normal life. The day from 8 in the morning to the evening, the nearby residents all appeared the instability of the mobile phone signal, "the phone just switched off, can not go out and do not come in." Ms. Du said. In this regard, some people believe that if the mobile phone shielding device is not allowed to strike, it may delay the emergency call, resulting in serious consequences. Reporter Yang Haitao



Reflecting the delay in the business of the phone



"Today, students from Jimo one middle school took part in the examination. As a result, my cell phone was cut off again, so I could not dial in. At the end of the exam, my cell phone received eight or nine short messages from the phone. Fortunately, it wasn't too important. If there was a very important leakage, who was the responsibility? " Yesterday afternoon, Ms. Du, who lives in Jimo, telephoned our newspaper reporter, saying that the school used mobile phone signal shielding device to make her cell phone out of order.



There are not only a few people who have suffered the same experience with Ms. Du, but reporters learned that there were thousands of residents living near schools, and their phones were jammed yesterday.



"I still find it strange that there is not a phone call today, and at least a dozen calls a day." The owner of a water supply station near Jimo's first middle school told reporters that in the past, she could receive phone calls for water every day, many forty or fifty, and at least seventeen, eight. But she didn't get one yesterday. "Does this delay business? You know, I have to install a plane, otherwise it will affect business. " The boss said it in helplessness.



School starts shielding against cheating



Yesterday, the reporter consulted with Jimo one. A staff member of the office told reporters that their school did have a cell phone signal shield, which was used yesterday, because there was a more important test yesterday. "Today this test is the first simulation test of the senior three students in the city. It is very important, it can be said to be a preview of the college entrance examination." The staff said that, in order to take the examination discipline seriously, prevent cheating, and thus ensure the impartiality of the examination, so as to provide an objective basis for the teaching after the school, they used the cell phone signal shield.



"Nearby residents have also reflected to us. We didn't expect the mobile phone signal shield to have such great power and the scope of radiation would be so wide. We will be very cautious when we use it in the future. " The staff said that under normal circumstances, they only use the mobile phone signal screening device in the national college entrance examination, the entrance examination and the national college entrance examination.



For the school's statement, Ms. Du said that he hoped the school would be able to make a notice when using this kind of shield. If it could put up a notice in the surrounding area, let everyone have a preparation.



General installation in the middle school



Do other schools have such a mobile phone signal shield? Yesterday, the reporter consulted the City Education Bureau, the relevant staff told reporters that the cell phone signal shield in the school is allowed to use, this is the Ministry of education and other departments of the student examination of a hardware requirements, like electronic monitoring, every secondary school should be equipped. The mobile phone shielding devices of various secondary schools in our city are uniformly provided by the educational department. But the staff also stressed that the mobile phone signal screening device can only be used in the examination, not allowed to use the exam.



"Yesterday's senior high school simulation test is a very important examination. This time, we need to use the mobile phone signal screening device." The staff said. As the phone signal shield affects the use of nearby mobile phones, the staff members think, "this cell phone shield should have nothing to do with the classroom."



But the reporter learned from the distributor of the cell phone signal shield that the size of the shielding range depends on the location and frequency of the shield, and the scope of the shield is round, not in the room or in the outside.



Signal shield



Five shields cover more than 10000 square meters



What is the working principle of the mobile phone signal shield?



In this regard, the city radio management committee office staff said, in fact, the principle of cell phone signal shield is very simple, it is to use its frequency to affect the frequency of the cell phone signal, white is like speaking, "loud noise".



"If two people are talking, how can they keep their voices down? The answer is very simple, as long as the third speakers speak in a bigger voice. The cell phone signal shield is the third. " The staff explained that the mobile phone signal shield is essentially a radio transmitter. On the working principle of the cell phone signal shield, the seller on the Internet has such a professional description: the working principle of the mobile phone is in a certain range of frequency, the cell phone and the base station are connected through the radio wave, and the transmission of data and sound is completed by a certain baud rate and modulation. In view of the principle of communication, the mobile phone shielding device will scan from the low end frequency of the channel to the high end at a certain speed. The scanning speed can form messy code interference in the message signal of the mobile phone, so the mobile phone can not detect the normal data from the base station, and can not establish a connection with the base station.



The reporter learned that through the use of "multiple honeycomb" installation, the radiation range of the cell phone signal shield is much larger than that, and the coverage of the five shields can reach more than ten thousand square meters.



Management regulations