Can take two simple methods.
1, a stainless steel teacup to put the phone in the lid, others call your phone will hear the phone you dialed is not in the service area or temporarily unable to connect please dial again later.
2, adjust to the flight mode.
Cell phone signal blocking devices
There are many kinds of cell phone signal blocking devices, generally handheld, wearable, and transmitter type. The general range of commercially available cell phone signal blocking devices is 500 meters.
Cell phone signal shielding equipment working principle: is through the cell phone signal shielding equipment issued by some other bands of the signal, the cell phone communication signal search and interference, so that the phone is not able to connect with the normal communication base station. Achieve the purpose of not receiving or sending information and making calls normally. Cell phone signal shielding equipment is generally used for large-scale exams such as: college entrance exams and national civil service exams, as well as state secret projects. For example: the military industrial enterprises new product development and other purposes.