Wireless Alarm System means Detectors /Sensors will send alarm signal to control panel via radio. It is much convenient to install without wiring. But the open communication channel also caused problems of easy interference, high rate of fault etc. Moreover, the alarm signal of address and data code are easy to be detected and decoded. Even wireless remote is more easy to be copied and set disarm illegally. Manufacturers were aware of this problem, and updated data encoding technology suchh as scroll code, encryption etc. Meanwhile, manufacturers developed more convenient installation of keypad zones or bus zones and expand module for the alarm system.