home security systems

Are wireless home security systems safe? Info from the Brickhouse Security say "Wireless Home Security Systems are fully wireless and have built-in power supplies; even if the phone, power and Internet connections are down, your Wireless Home Security System will continue to monitor and protect your property. This feature will come in handy if an intruder cuts the power and phone lines, or there is a blackout and burglars are on the prowl." Does this mean that the system has its own cell-phone built-in or uses a satellite so it could notify the PD and if so doesn’t a burglar need nothing but a signal disrupter? No I’m not a burglar, just curious in how it works and how safe it really is. We all know if you have an alarm set to the phone-line someone can cut the lines, if you have digital phone someone can just turn the power off your house, or do both. So can a disrupter knock out the system signals? The real question is, "How safe are any Home Security Systems?"