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.
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.