Common cell phone signal jammers on the market have operating frequencies: 869~894MHz; 825~960MHz; 1805~1880MHz and 1900~1990MHz, etc. The applicable frequency bands are CDMA800, GSM900, DCS1800, and PCS1900. It can control a range of about 40 meters in diameter, using a DC-DC converter input voltage and 5V output voltage. Before purchasing a jammer, there are several important...