How to jam a cell phone?
Perhaps you've heard that some libraries are already using a device called a cell phone scrambler. The main purpose of the device is to keep order and quiet on site, and to disable access to mobile phone signals. Imagine working in a quiet library， it is wonderful. You can concentrate on working in the library. You don't have to listen to loud ringtones and calls
I'm pretty sure we've all considered having one at some point: whether the obnoxiously loud woman next to you is announcing private bedroom stories to a crowd on the subway, or your kids are grounded from using the phone (and consequently snagged a hidden prepaid phone), sometimes having a cell phone jammer comes in handy.