Z-Com ZMAX-8210-I - Manual (Page 13)

Be sure to your ZMAX-8210 is connected the ground wire, preventing something
unexpected.
Antenna Installation
16dBi built-in antenna is placed in the ZMAX-8210, so you need not install antenna.
The ZMAX-8210-E needs an external antenna. You should choose your antenna as your need.
Warning：
Keep your ZMAX-8210 associated with the antenna away from power line, lamp,
electrified wire fence or anything others electrified.
Though a thunder-proof component is built in, it is recommended that additional
thunder-proof device is needed for effectively protecting your ZMAX-8210.
Chapter 2 Introduction - 7 -