Junhua there is no internal lightning arrestor. Please review the Motorola Solutions AP7161 Access Point Installation Guide (Part No. 72E-151062-01 Rev. A) available from support.symbol.com It mentions the following: While RF protection is a consideration, it shall only be required when antennas are connected to the node with coaxial cables greater than 610 mm (2 ft.) in length. Lightning protection should be used on all shielded CAT5E Ethernet connections. An outdoor rated Lightning Protection Unit (LPU) kit such as the Motorola Solutions PTP WB2978AA or the HyperLink AL-CAT6HPJW Lightning Protector should be used. More info on the sections: Grounding Requirements and   Ethernet and Lightning Protection Hope this helps.