Table of Contents
Advertisement
Chapter 4:
Overview
The OCM supports a variety of line interface modules (LIMs) which are the network-side interface
for the OCM. LIMs provide link synchronization and aggregate framing. In conjunction with the
CCM, a LIM can supports up to 2 subaggregates for each OCM. The 2 subaggregates maximum
can be supported in several different ways (for example, 2 LIMs supporting 1 subaggregate each or
1 LIM supporting 2 subaggregates.
A LIM can support the T1/D4/ESF connections for North American applications or the G.704
connections used in ITU-T countries.
•
The T1 interface is fully compatible with AT&T Pub. 62411. It will support a full 1.544
Mbps link speed, as well as fractional T1 rates in N X 64 kbps increments.
•
The E1 interface supports the 2.048 Mbps link rate and conforms to the ITU-T G.704
standard for N X 64 kbps links. Electrically, the E1 interface is per ITU-T G.703; and the
frame structure adheres to ITU-T G.704.
Redundancy Restrictions
Two LIM modules provide redundancy. The pair must be installed in an odd-numbered, even-
numbered pair of adjacent slots. Both LIMs must be connected to the line via a suitable cable. One
module is in-service and connected to the line, the other module is in a standby condition and is
disconnected from the line. If the in-service module fails, it disconnects from the line and the
standby module connects to the line as the in-service module to restore operation. The redundancy
switch must be set in the proper position:
•
S1 - REDN on the Network T1/E1 and Network T1 CSU LIMs
•
S1 - RD/NRD on the V.11, V.35, X.21 and Subrate LIMs
The front panel disable (Dsbl) switch can be used to perform a redundant switchover manually. This
is a momentary pushbutton switch. When pushed on the in-service LIM, the standby LED will light
to confirm that the switch was pressed. You must press the switch for at least one second. Then the
in-service LIM goes into standby and the standby LIM goes in-service. Note that the disable switch
on a standby LIM has no function.
Procedure for removing a LIM
To minimize disruption to the OCM, it is strongly recommended that you should put an in-service
LIM in standby before you remove it. If the LIM is non-redundant, you should still put it in standby
before removing it.
1. If the LIM is in-service, press front panel disable switch for at least one second. The standby
LED lights, and the LIM goes into standby.
2. Extract the standby LIM.
036R340-000
Issue 16
Line Interface Modules
Office Connunications Manager OCM-1000/OCM-2000
Installation & Operation
4-1
Advertisement
Table of Contents
