The Shanghai Grand Theater, which spent over $36,000 on an electronic jamming system to disable cell phones and wireless pagers in its performance space, is being forced to turn off the system after being told that using it is illegal. The theater says that it will begin politely asking patrons to turn off their mobile devices, which performers claim ring “from start to finish,” but some theatergoers insist that they should have the right to stay in touch with the outside world, even if it means disrupting the show.