In the prison cell phone signal jammer can be used to effectively control the offender contact with outsiders, so in these places use the phone jammers are legal.
Cell phone jammer is mainly equipment requires shielded 2G 3G 4G signal, it acts as a technical means, which has been present in the current society, many people use such devices.
GPS jammer can be installed in a vehicle. It allows GPS useless in some confidential within the company needs is a very important significance.
How to make a cell phone jammer? In China to buy a small module, so you have a test board, and can be assembled according to their needs a 4g jammer.
Knowledge: the signal is actually encrypted transmission of electromagnetic waves, the signal peaks and troughs on behalf of 1,0. cell phone jammer play a superposition of waves, resulting in the shielding effect.