How does the signal blocker block the signal and how does it work?

     Nowadays, it is very common to install a cell phone signal blocker for the college entrance examination. Its working principle is that when sending and receiving information on your mobile phone, the mobile phone signal blocker is equivalent to a very powerful cheerleading team, shouting loudly and making a very loud sound. The "noise signal" is so loud that your mobile phone can't hear it, and the "mouth" also shouts but the signal blocker. In fact, it is very simple to understand. This is not to block your signal, but to directly interrupt the connection between your mobile phone and the base station.

In fact, you can understand that you are whispering with your friends, and suddenly 20 teenagers playing rap come and sing their high notes. At this time, you will find that you can't hear what your friends say for a while. No matter how the mobile phone is upgraded, it needs wireless network equipment, and an invisible network cable is needed to connect it. This invisible network cable is the operator's communication base station. When using a mobile phone, whether it is making a call or sending a text message, it is necessary to get in touch with the nearest communication base station in the surrounding area. If you hold a mobile phone in each hand and use the mobile phone in your right hand to call the mobile phone in your left hand, the radio waves of the mobile phone are not as simple as transmitting from the right hand to the left hand immediately, but will be transmitted from the mobile phone in the right hand to the mobile phone base station 500 meters away, and then make a big circle to transmit back to the mobile phone in the left hand (except for the Bluetooth function). Under normal circumstances, the base station and the mobile phone are chatting in full swing, sending electromagnetic wave signals to each other freely, but once the signal blocker is turned on, it will "beat the drums and gongs" next to the mobile phone, and send out "noise" electromagnetic wave signals that are many times more powerful than the received base station signal. The mobile phone cannot hear what the base station is saying and cannot receive the signal of the base station normally. The connection between the two is disconnected, and the mobile phone will become a deserted island. Whether it is making a call, sending a message or other various functions, it is in a paralyzed state.

In the state of so much noise, not only the signal of the examination room is "blocked", but also the wireless signal near the examination room will be affected, which seriously affects the call quality of mobile phone users near the examination room. Does this signal blocker really work? The entire frequency band of radio waves ranges from a few Hz to tens or hundreds of GHz. Each band may be used as a communication signal. However, except for a small number of very good machines, ordinary signal jammers are "not loud enough" and "tone deaf". A signal jammer can only block a small part of the frequency band, and communication tools can use the unblocked frequency band to communicate. Of course, many telecom operators in China have 2G, 3G, and 4G mobile phone services. The increase is really concentrated in a few small frequency bands. The signal jammer in the examination room needs to take multiple measures to solve this frequency band.

When the mobile phone signal jammer is resting, it will "shoot" messy radio waves from low frequency to high frequency in each frequency band, affecting the connection between the mobile phone and the base station. The mobile phone signal jammer basically makes the mobile phone unusable, but the violator can still use his own communication tools. The seller of answers has a special radio transmitter in his hand, and the student has a wireless communication signal receiver in his hand (most of the communication tools currently sold on the market are of this type). The frequency band used by this illegal communication tool can be selected outside the frequency band range that the mobile phone signal jammer can reach, and often infringes on the dedicated frequency band of wireless walkie-talkies. For example, some students use built-in earphones to receive test answers transmitted by wireless communication. Sometimes these earphones are very small and must be taken out of the electromagnetic field. If not, a doctor's help is needed to take it out. Or, the receiving module and other electronic products are hidden in the temples. However, the devil is always better. There is a wireless communication detector that can help to solve the electromagnetic wave data signals in those frequency bands, and the signal jammer on the mobile phone cannot be ignored.

Before the exam begins, the signal strength of various illegal electromagnetic wave devices such as mobile phones, radio programs, and televisions around the exam room are processed. After the exam begins, the wireless communication detector in the car, the trunk, and the office is running, which can receive all signals in all electromagnetic wave frequency bands. When the tool starts to send answers to the exam room, the detector will "empty a piece" of unknown electromagnetic wave signals, and the tool's signal cannot escape the precise detector ear. When students are in the examination room, when the two parties inside and outside the examination room communicate, the "precious information" such as answers ABCD will first be converted into binary numbers and numbered. If necessary, it will be encrypted, and then the electromagnetic field of the used wavelength will be adjusted to load the information into the radio wave signal, which will be transmitted by the wireless antenna of the transmitter. The other party in the examination room will perform encoding and decoding adjustment to restore the ABCD information. However, with this wireless detector, the signal transmission method used by both parties can be clearly understood within a few seconds. Not only can the signal be detected, but the information inside can even be directly extracted to hear what is said in the conversation. No matter how high-precision the machine used by the offender is, the nature of "parallel perspective" of radio waves must exist. With the help of several detectors placed in different positions, the location of the signal transmitter can be calculated according to the distance and signal blocker, and the sender of the answer can be caught on the spot.