255-700-025
2-3
PacketStar
™
Access Concentrator 60 User Guide
, Issue 1
Release 6.3.0
Chapter 2 Hardware Description
Chassis Architecture
of the chassis faceplate has controls and indicators for the common
equipment components (see Figure 2-1).
The chassis backplane distributes data, clock signals, and power to the
modules. From the Power Supply component, the backplane distributes
+5 V dc of power for logic circuits; -48 V dc for voice, cooling fans, or other
applications; and 2.1 V dc for bus termination.
The backplane architecture consists of a single bus, which supports 600 Mbps
of ATM bandwidth, and “live” insertion and removal of the I/O and server
modules. In conjunction with the Stratum 3–4 component, this architecture
provides the basic ATM concentration technologies of the AC 60 system. The
backplane is based entirely on switching ATM cells.
Stratum 3–4 Clock Timing
The Stratum 3–4 component provides synchronization and monitoring for
the AC 60 system. This component supports the backplane bus and furnishes
600 Mbps of ATM bandwidth. In addition, the AC 60 system can obtain
network clock synchronization through the backplane from any of its I/O
modules except for the DSP2A/B/C Voice Server, Ethernet, High-Speed,
Tones and Announcements Server, Route Server, Voice 2-Wire Station, and
Voice 2-Wire Office modules. The Multi-Serial module can be used for
network timing, but it is not recommended. With the ability to accept a
timing reference from any physical interface at low transmission rates, the
system provides the network with a reliable transport and access
infrastructure. The Stratum 3–4 clock timing is accurate to Stratum 3
requirements, allowing the AC 60 system to freely run even after losing
external synchronization, for as long as 24 hours, without synchronization
problems.
!
CAUTION:
The external synchronization interface port provided on the Stratum 3–4
module is intended only to be connected to an in-building reference
Figure 2-1. AC 60 System Chassis
110-127VAC4.OA
50Hz
ACTIVE
FAIL
CLOCK LOSS
EXTERNAL
SYNC.
ON
OFF
POWER
ETHERNET CONSOLE
KEY
J4
J3
J2
J1
Access Concentrator 60