Polycom SpectraLink 1725-36028-001 - Manual (Page 33)

Install SpectraLink 8000 Telephony Gateway
All system units must be grounded to a protective earth by means of
the grounding stud located on the rear panel. Refer to the illustration
below for recommended continuity connection.
No more than 15 units may be grounded through one connection to
the protective earth ground. Systems involving more than 15 units
must be broken up into groups of 15 or fewer units with each group
provided with an independent protective earthing conductor.
PN: 1725-36028-001_T.doc 33