This is a very efficient device, portable and practical, with antennas. Whether I'm on a train, in a movie theater, or anywhere else where the use of a cell phone is prohibited, the mobile phone owner will be surprised to find that their cell phone is out of network within 10 to 15 seconds after turning on the cell phone jammer.
This jammer is a great tool. Very reliable, and will interfere with GPS navigation and mobile phone signals, with good jamming range and a long service life. I tied it to a belt and let myself work easily.