The unit will shield you from the noise and disturbance of cellular phone calls, within an effective area of approximately 500square meters. Ideal for use in detention centers, classrooms, factories, convenience stores, gas stations, and other locations fixed continuous non-stop cell phone jamming is required. CDMA:869-894MHZ GSM:930-960MHz DCS:1805-1880MHz, PHS:1900-1925MHz 4 channel types,can efficiently provide shield for mobile signals from GSM,CDMA,DCS and PHS Coverage 500sqm We can supply different frequencies,different coverage jammer to suit different customer need