Polycom RMX RMX 4000 Hardware Manual page 38

Chapter 1- Hardware Description
1-30
Table 1-8 RMX™ 4000 Slot Numbering
Slot ID/No. Card/Component
12 Fan Drawer
13-16 RTM ISDN/RTM
LAN
17 RTM-IP 4000
18 Blank Panel
19-21 Power Modules
Requirement
Mandatory
Either an RTM ISDN or an RTM LAN
card is mandatory in combination with a
Media card. The RTM ISDN/RTM LAN
board must be inserted in a slot opposite
any MPM+ card.
Mandatory
Not Available (NA)
Mandatory: 
With AC power, 3 power supplies are
installed, with the 3rd redundant.
With DC power, 2 power supplies are
installed with the 2nd redundant. The
center slot (#20) on the rear of the RMX
4000 is disabled and is fitted with blank
panel.
Note: Protective bonding conductor size
is 14AWG (1.5mm) within the Power
Entry Model.