Shulou(Shulou.com)11/24 Report--

Cold window studied hard for more than ten years, when the title of Jinbang was once. The college entrance examination is always a big day for the whole people to pay attention to. Apart from paying attention to the composition questions every year, I wonder if you have considered how to prevent candidates from cheating in such an important big examination as the college entrance examination.

In the news after the college entrance examination, we often see individual candidates who are hot-headed and want to take advantage of all kinds of "crooked ways" to challenge the fairness of the examination.

For example, through special glasses, you can see the text on the watch screen, the glasses watch "set".

For example, the "eraser" that can display the answer.

For example, button cameras, cheating pens and so on. All kinds of high-tech cheating tools emerge one after another, and even some examination rooms have introduced high-end cheating tools from abroad-espionage equipment.

I haven't seen these tools either, but I was shocked. As a communications engineer, Mr. Archive just wants to tell you that all these crooked ways cannot escape the eyes of invigilators.

Some candidates think that as long as the phone is turned off and placed in a "well-designed" place such as the sole of the shoe (you know), you can escape the scan of the metal detector waved by the invigilator at the entrance of the examination room and successfully bring the phone into the examination room.

As everyone knows, if the mobile phone does not have a signal, it is not even as good as a brick.

Why? It also starts from the working principle of mobile communication.

01. The working principle of Mobile Communication Mobile phone, as a mobile communication device, needs to establish a connection with the nearby base station before accessing the core network to find the communication destination.

In this process, all information is carried and transmitted by electromagnetic waves. The frequency band of the electromagnetic wave used by the mobile phone is related to the standard used by the mobile phone and the operator. But generally speaking, the electromagnetic wave bands used by the three operators are distributed in the range of 850-4900MHz. Although we want to block the mobile phone signal in the examination room, it is impossible to make all the base stations near the examination room not working at the same time, otherwise all the communication equipment in this area can not be used properly. That being the case, the only way left is to block the cell phone signals in the examination room.

When it comes to blocking cell phone signals, the first thing that comes to mind is metal shielding, that is, the phone is placed in an airtight metal box to block the propagation of electromagnetic waves through metal. But it is obviously not practical to make all the classrooms in the examination rooms into metal-enclosed classrooms.

What are we going to do?

Simply, you only need a small cell phone signal blocker to block all mobile phone signals in the examination room.

02. The principle of shielding the mobile phone signal the mobile phone signal shielding device scans the low frequency section of the forward channel (from the base station to the mobile phone) to the high frequency band at a certain speed, and forms interference in the process of receiving the message signal by the mobile phone. so that the mobile phone can not detect the normal data sent from the base station, thus unable to establish a connection with the base station, showing no signal, no service.

For example, when the mobile phone communicates with the base station, the signal blocker is like a troublemaker, deliberately making noise near the phone, so loud that the phone can't hear what the base station is saying. And the base station can't hear what the phone says. In fact, this is not to shield the mobile phone signal, but to make the mobile phone signal annihilated in a large number of noise signals, so as to achieve the purpose of interference.

At present, the mobile phone signal blockers used in the examination room are all full-band, it can interfere with all the frequency bands of 2G / 3G / 4G / 5G of the three operators, and WIFI signals and Bluetooth signals can also be completely shielded.

Therefore, it must be impossible for examinees to cheat on their mobile phones. However, the frequency band of electromagnetic wave ranges from several Hz to hundreds of GHz, and each band may be used as a communication signal. So, will there be some special frequency bands that will be used in the examination room?

Although other wireless communication tools are surprised, it is true that some wireless communication tools use a dedicated frequency band.

Those who sell answers to the college entrance examination in the news have such equipment in their hands. The working frequency band of these devices is selected outside the frequency range covered by mobile phone jammers, and illegal candidates use mini headphones to listen to answers during the exam. The signal receiving module of this mini headset is usually hidden in the glasses frame.

However, under today's anti-cheating measures, the glasses frame is no longer an "out-of-law place". In view of this special radio communication tool, the examination room is specially equipped with a monitoring vehicle equipped with a radio monitor for real-time monitoring of radio waves from unknown sources.

As the electromagnetic wave has the characteristics of "near, big, far and small", by constantly moving the detection vehicle, the monitoring equipment can locate the position of the signal transmitter according to the distance and the strength of the signal, and catch the answer sender on the spot.

Nowadays, drones also appear in all kinds of large-scale examination rooms, which can locate the signal more quickly.

All kinds of large-scale examinations are not only the stage of knowledge competition for the majority of students, but also the contest of cheating and anti-cheating technology in the communication circle. The so-called as vice rises one foot virtue rises ten, although all kinds of cheating methods emerge one after another, but the anti-cheating technology can be better. There is no difference between good and bad communication technology, but some people use them in the wrong place.

Just as communication engineers guard the world's communication network all the time, there are many staff who silently guard the candidates in the annual college entrance examination. With the level playing field constructed by these guardians, please focus on the examination papers in front of you and write down your unforgettable answers on your life journey with real knowledge.

Tomorrow will usher in the annual college entrance examination, and millions of candidates will usher in a crucial moment in their lives. Mr. documentation wishes you all the best in advance.

This article comes from the official account of Wechat: ZTE documents (ID:ztedoc)

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