Special venues such as examination rooms and prison cells will use full-band signal jammers or devices that shield mobile phone signals, so that communication with outsiders can be effectively avoided.
https://www.dojammer.com/cell-phone-jammers.html

The basic principle of the jamming device is to emit the same radio frequency signal as the mobile phone. Since the frequency is the same, the mobile phone cannot distinguish which signal is a conventional base station signal, thereby achieving "jamming". As long as there is a machine with the same frequency as the phone, when the base station tries to connect to the phone, there will be a lot of "noise", and you will find that the signal from the phone cannot be recognized.
https://www.dojammer.com

If you found a tracking device around you, would you figure out how to protect yourself? Of course, the answer is yes, and it needs to be. So, you know what kind of tracking devices are used nowadays to track people, if you search the internet, you will find that GPS signal tracking devices and cell phone signal tracking devices are being used now, if you want to know about devices called cell phone jammers and GPS jammer, and can help you avoid being tracked, then it's worth stopping to look at the details, then you'll clearly make the best choice.
https://www.dojammer.com/gps-blocker-jammers.html

In daily life, there are many places, such as examination rooms, conferences, prison cells and other areas, where it is very unsuitable to use electronic equipment and communication equipment at will. Just use a wifi jammer.
https://www.dojammer.com/wirel....ess-wifi-blockers.ht

This portable GPS gsm jammer can not only interfere with GPS L1 (1570-1580 MHz), GPS L2 (1220-1230 MHz) signals, but also interfere with 2G, 3G, 4G and WiFi signals. The interference radius is between 2 and 20 meters. The charging process can work continuously for two hours and can be used while charging.
https://www.dojammer.com/cell-phone-jammers.html