Technical data

3-4
Extended XR Chassis
3
20-slot System
The Model XR9120A 20-slot system (see Figure 3-2 on page 3-5) is
designed for telecom applications requiring 20 VME slots and up to
100GB of disk storage capacity.
A Model XR9120A 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 -36 to -72 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
XR9120A 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 will
continue normal operation if a power module fails.
The XR9120A 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.