Arrestor

What's the best arrestor can be used to protect the telephone lines from the lightning surgges?
Thanks

Unplugging it.
Seriously.

Gas discharge types are probably the best, as is proper grounding, BUT...
No arrester will last forever; one strike is likely to take them out, leaving the circuit unprotected, and with no indication.

Lightning rods may help, if it's a serious problem.

If safety is a concern, isolate the internal telephone system from the external with an optical (fiber) interface. Of course, that can be costly.

What is the optical (fiber) interface? more details about it is highly appreciated.
regards

Mosab,

Take a look at this link: http://www.citelprotection.com/citel/telephone_RJ.htm