Mastering the stick, but aiming for the yard. There is a kind of radio monitor that can help fix the electromagnetic wave signals in those frequency bands that the cell phone jammer does not take care of. Before the start of the test, the signal strength generated by various legal radio wave devices such as mobile phones, radios, and televisions around the test room are recorded in the test room. After the test starts, in the car, suitcase, office, and radio monitors. Start all together, you can receive all the signals of the entire radio wave frequency band. When the cheating tool starts to send answers to the examination room, there will be an "extra piece" of radio wave signals from an unknown source on the monitor. The signal from the cheating tool is difficult to escape. Through the ears of a sophisticated detector.
When the examinee cheats, when the sending and receiving parties inside and outside the examination room communicate, the “valuable information” such as ABCD answers must first be converted into binary numbers, encoded, and encrypted if necessary, and then the electromagnetic waves of the used band will be processed. Modulation, the information is loaded on the electromagnetic wave signal, which is sent out by the antenna of the transmitter, and the other party in the examination room decodes and demodulates to recover the ABCD information. However, with this wireless detector, it is possible to get a clear picture of the signal transmission method used by both parties in the cheating technique within a few seconds. Not only can the signal be detected, but the information can even be extracted directly and heard in the conversation. Say what.
No matter how sophisticated the equipment used by the cheaters, the nature of electromagnetic waves "near big and far small" must exist. Relying on multiple monitors placed in different positions, the signal can be calculated based on the distance and the strength of the signal. The location of the launcher, capture the answer launcher on the spot.
At present, the more feasible method from the perspective of technical products is to install mobile phone signal jammers at appropriate locations in the factory. Each mobile phone portable jammer can cover a certain area, and these coverage areas can be formed into areas in a cellular network. The coverage to achieve complete signal shielding in large areas. The current mobile phone signal jammers are all full-band. It can shield all the 2G 3G 4G signals, 2.4G WIFI signals and Bluetooth signals under all the three operators of China Mobile, China Unicom and Telecom. Its principle is sent by itself. The frequency interferes with the mobile phone receiving the frequency sent by the base station and the wireless router, so as to achieve the purpose of shielding them.
The working principle of the signal jammer: In a certain frequency range, the mobile phone and the base station are connected by radio waves, and the data and sound transmission is completed with a certain baud rate and modulation method. The jammer scans from the low end frequency of the forward channel to the high end at a certain speed during operation. This scanning speed can cause garbled interference in the message signal received by the mobile phone. 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 and achieve the purpose of shielding the mobile phone signal. No service system and other phenomena.