How to crack the working principle of the mobile phone signal shielding device in the college entrance examination examination room?

There are generally two ways to block cell phone signals:

One way is the same as the principle of closed-circuit television. Put the mobile phone in a metal mesh bag, and in principle all electromagnetic waves will be shielded.

Another is that if you walk into an area, the mobile phone will have no signal. This is because there is an electromagnetic wave transmitter in the area. Its frequency is the same as that of the mobile phone. The signal it emits interferes with the signal of the mobile phone.

The cell phone jammer currently on the market work in accordance with the second method. In fact, the principle is very simple, but private use of this frequency band is illegal and cannot generate commercial value, but now schools are starting to use it to prevent cheating. Let’s take a look at its working principle.

When the mobile phone is working, it is within a certain frequency range. The mobile phone and the base station are connected by radio waves, and the data and sound transmission are completed with a certain baud rate and modulation method. In response to this communication principle, the mobile phone signal jammer scans from the low-end frequency of the forward channel to the high-end at a certain speed during operation. The scanning speed can cause garbled interference in the message signal received by the mobile phone, and the mobile phone cannot detect the normal data sent from the base station, so that the mobile phone cannot establish a connection with the base station. The mobile phone is manifested as a search network, no signal, no service system and other phenomena.

How to crack?

First of all, I feel shameless about this title because it has no solution. I am actually telling everyone how to avoid it?

Method one (very silly and shameless): When entering the examination room, secretly turn on the shield while the teacher is not paying attention. At the beginning of the exam, the teacher will habitually turn on the shield, because the shield itself is turned on, so… it will be turned off!

Method two (luck): WIFI, WLAN unlimited local area network functions only available in smart phones, turn on wifi, wlan and other devices, search-connect-confirm-enter the password (default password 12345678). According to experience, all routers like to use the wifi password The setting is the same as the username, you know. (Because many jammer products in the market do not shield and interfere with the 2.4G frequency band of WIFI)

Method three (tips): When the mobile phone has no signal, click Settings-Network-Network Selection-Manual-Searching Network-Select Network (China Mobile/China Unicom/China Telecom) Speed ​​select the type of card you use, speed exit, so Short-time signals can be obtained. This method consumes more power because it needs to search the Internet.

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