Enmac Engineering Limited developed mobile phone signal jammer by using the currently advanced high-frequency signal microcomputer controlling technology. This high-tech instrument is capable of isolating all sorts of signals GSM,CDMA,DCS & PHS, makes the mobile phone losing its ability to sending and receiving signals. Such instruments are widely used in those quiet and confidential occasions as the conference rooms of armed force, exam and governmental agencies and other secrecy, and locale of Director of Boarder meeting, scientific research units, training center, press conference, theater, music hall, church, mosque, hospital operation room, patient's room, petroleum station, liquid gas station and inflammable places which mobile phone calls are prohibited.