Technical data

Chassis Overview
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2
20-slot System
The Model XR9120 20-slot system (see Figure 2-4 on page 2-8) is
designed for telecom applications requiring 20 VME slots and up to
100GB of disk storage capacity.
A Model XR9120 system typically uses a VME drive module for the
initial 3 1/2-inch disk and tape. Additional drives are added using
a SCSI Device Storage Module (see Chapter 4). Up to 13 Storage
Modules can be added to each system. Each Storage Module
contains up to four half-height drive bays. Two of these bays can
contain removable media devices. Each system can support up to
52 SCSI drives.
The XR Series offers a -48±10% (-36 to -72 with the MC1000K-
DC700A—see Chapter 7) VDC power module for telecom exchange
office applications, as well as a 90 to 264 VAC autoranging power
module for industrial and commercial environments. The XR9120
supports either single or dual power module configurations. When
dual power modules are configured, they run in load sharing
mode. In load sharing mode, the system can continue normal
operation if a power module fails. For more information about load
sharing, refer to Load Sharing on page 7-12.
The XR9120 enclosure contains 21 transition module slots for
supporting a variety of connectivity and expansion options, such as
additional Ethernet, SCSI, and communications interfaces.
The XR Series includes a unique VME and transition module pair
keying feature which prevents potential module damage caused by
the incorrect insertion of VME or transition modules.