Where is the GSM mask used

-
HelloI learned about this kind of device on the Internet. I only know it can interfere with GSM signal, but I don't know where to use it. Can you tell me where this kind of equipment is needed?
If you want to know the frequencies of your country, we can offer you some help:

The proliferation of mobile phones has also brought many problems. Cell Phone Jammer For Drone prevents all possible accidents.

School examination rooms, prisons, detention centers, etc., to ensure fairness and justice in examinations, high school entrance examinations, college entrance examinations or usual mock examinations. So how to choose Cell Phone Jammer News?

Many friends have consulted the waterproof bumper. We have a powerful portable cell phone jammer that can meet your requirements, is easy to install, and has a waterproof function, you can install and use it anytime, anywhere. This kind of waterproof mobile phone signal jammer can effectively block Bluetooth 3G 4G WIFI GSM mobile phone signals.