Today's schools, in order to prevent cheating on mobile phones, will use blockers to block mobile phone signals when they come to exams. So how to block it? What is the principle?

First we need to understand how mobile phones work. When the mobile phone is working, within a certain frequency range, the mobile phone is connected to the base station through radio waves, and completes the transmission and exchange of data and sound with a certain baud rate and modulation method.

Since it is connected by radio waves, shielding is very simple. As long as I interfere with the radio waves of the communication, the mobile phone cannot be used normally, and the purpose of shielding the signal is achieved. The principle of the shield is probably the same.

The cell phone jammer scans from the low-end frequency of the forward channel to the high-end frequency 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 searching the network, no signal on the mobile phone, no service system, etc.

Blockers can block signals in many frequency bands. Mainly can effectively shield CDMA (China Telecom), GSM (China Mobile, China Unicom), SCDMA (Netcom Dalingtong), DCS (1800MHz), PCS (1900MHz), PHS (Telecom PHS), 3G mobile phone signal, WIFI and 4G mobile phone signal and other communication signals. Can be purchased on demand.

Some people will think this thing has radiation. The power of the general shield is not very large. The transmission power is about 1 W ~ 16 W, so it will not be harmful to human health. Remember to close it when not in use. Otherwise, it will affect the use of normal mobile phones in the surrounding area and cause complaints from operators.