Mobile jammers create a quiet classroom environment
"In order to prohibit senior high school students from using mobile phones in class, each classroom must turn on mobile cell phone jammer." Recently, many parents posted online reflecting that they worried that this practice of Jiangxia District Experimental High School would affect their children's health.
Yesterday morning, the reporter saw in Jiangxia District Experimental High School that there is a mobile phone jammer on the upper right of the blackboard in every senior middle school classroom with 4 antennas on it.
A student in the third grade of high school introduced: "After the new semester begins, the school requires the mobile phone jammer to be turned on during the third grade. The students stay in the classroom every day and have had adverse reactions such as dizziness."
The students said that the school adopted this move to create a quiet classroom environment, everyone can understand, but for a long time to study and live in the radiation environment of mobile phone jammers, worrying that their health will be affected.
During class yesterday, the reporter walked into a number of third-year classrooms and found that the mobile phone signal was normal and there was no shielding interference. Some students said: "It's just that the jammer has not been turned on in the past two days."
Jiangxia District Experimental High School Vice Principal Chen responded that the school is a test site for the college entrance examination. In October last year, mobile phone shielding devices were installed in 60 classrooms in the school. They are generally used for large-scale exams such as final exams to prevent candidates from cheating. He denied using the shielding device to maintain classroom order in the third grade, saying that he would not use the shielding device during class.
It is understood that mobile phone jammers, like mobile phones, emit electromagnetic radiation. my country has a national standard for electromagnetic radiation protection: the electromagnetic radiation power density accepted by the public in the environment is less than 40 microwatts/square centimeter, which is safe. Both environmental protection departments and environmental health research institutions can do such tests.
Regarding why mobile WI-FI Internet access can break through the "shielding barrier", the reporter made a special consultation with Chen Zhuo, an engineer engaged in the research and development of communication products. According to his introduction, the working principle of the mobile phone shielding instrument is to scan from the low-end frequency of the channel to the high-end frequency at a certain speed, and it will repeat itself. This scanning frequency can cause garbled interference in the message signal received by the mobile phone, and the mobile phone cannot detect normal data sent from the base station, so that the mobile phone cannot establish a connection with the base station. The mobile phone shows the phenomenon of repeatedly searching the network and no signal to achieve the purpose of shielding.
"At present, the mobile phone frequencies of major telecommunications operators are concentrated around 800MHZ, 1800MHZ, 900MHZ and 1900MHZ, and very few reach around 2100MHZ. This is why the current shielding instruments have launched the above-mentioned four shielding frequencies tit-for-tat." Chen Zhuo The engineer said, but as a wireless network connection standard, WI-FI has frequencies of 2.4GHZ and 5GHZ, and its frequencies are beyond the interference range of the mobile phone scrambler. This is when the mobile phone is interfered with no signal, turn it on The reason why the WI-FI function can still get the signal from the wireless router.
The reporter then learned from relevant parties that the shielding devices currently used in some schools also have an "enhanced" built-in antenna, most of which were purchased after 2008. However, after consulting the relevant information of this type of "enhanced" shielding instrument, the reporter found that the shielding frequency range is still mostly 800MHz, 900MHz, 1800MHz, and 1900MHz, and will still be helpless in the face of wifi.