If they detect something wrong while the system is armed, they'll transmit a wireless alertsignal to a base station that will then raise the alarm.
如果他们在系统布防时发现了什么问题，就会向基站发送无线警报信号，然后基站会发出警报。
2
With the right device tuned to the right frequency, what's to stop a thief from jamming your setup and blocking that alertsignal from ever reaching the base station?