DX-151

4 Mode:Chime , Alarm off , Instant Alarm & Delay Alarm. Pleasant "Ding-Dong" sound as chime. Built-in loud 110 dB siren. Arm/Disarm alarm by 4 digit changeable secret codes. Panic button to activate alarm without door opening. Magnetic sensors at both sides (left & right)to reliably detect the door opening. Alarm reset automatically to detect another intrusion. No Wiring require,DIY,easy-to-install burglar alarm. Power: 3*"AAA"(UM-4) Batteries.