"Specification: 1.It can restrict the mobile phone signal which is 40m-100m in diameter and 200 meters far from the transmitting station. 2.It only shields mobile phone signals, but has no influence on other electronic equipments, audio equipments and human bodies. 3.It is easily installed and the connector plugs is the only one what is needed to install. 4.It saves the electric energy. 5.Working frequencies: 860-885MHz, 930-960MHz, and 1.800-1.99 GHz. 6.Working frequency bands: CDMA800, GSM900, DCS1800, and PCS1900. 7.For school,theatre,church,hospital,etc."