Point-to-Point Delivery of T1 Circuits Using MM840L - Charles ...

Application Note – Point-to-Point Delivery of T1 Circuits
Using MM840L
Application
This application note describes a point-to-point application for the Mini-Mux 840L. The
Mini-Mux 840L (“L” stands for “Lite”, hereafter referred to as MM840L) multiplexes 28
T1 circuits into an OC-3.
Description
The goal in this application is to deliver up to 28 T1 circuits from the Central Office to a
Remote Location. Obviously the 28 T1 circuits can be connected between the two
locations with copper pairs. However, 28 T1 circuits would require 56 copper pairs, in
addition to office repeaters, and possibly field repeaters, depending on the length of the
circuits.
Historically this application has been handled using Lucent DDM 1000/2000 equipment,
as shown in Figure 1. However, there are disadvantages to this arrangement that the
MM840L overcomes, namely space, power consumption, and cost.
Fort Bragg: Point-to-Point T1 Delivery
Lucent DDM 1000/2000
Central Office
Remote Location
Voice
Switch
T1s
DDM
1000/2000
OC-3
1+1 APS
DDM
1000/2000
T1s
DMX
DDM 1000/2000
Over 6 RU (10.5”) of vertical rack space
Large power consumption
Costly
Limited remote management options
Figure 1 – DDM 1000/2000 for delivery of T1 circuits
Page 1 of 3 10/4/2005

Figure 2 shows this application using the Mini-Mux 840 Lite instead. One of the biggest
advantages is the space and power savings. The MM840L is only 1 RU (1.75”) in height
and draws a maximum of 35 Watts of power.
Another key advantage is the integrated test features. The MM840 can do a number of
different loopbacks and diagnostics functions for troubleshooting T1 circuits and/or the
OC-3 link, such as
• local (near-end) T1 loopbacks
• T1 NIU/CSU loopbacks, with user configurable loop-up/down bit patterns
• C-bit loopbacks, to loopback a single T1 within the OC-3 payload
• OC-3 loopback, for looping the entire OC-3 payload
• T1 test pattern generator and receiver for doing BERT tests without the need for
external test equipment
In this application, each MM840L was configured for T3 C-bit multiplexing. That is, the
MM840 multiplexed the T1 circuits as T1T3STS-1OC-3. Referring to Figure 2
then, the Local Unit (located in the Central Office) can send a C-bit loopback request to
the Remote Unit for a particular T1 circuit within the OC-3. Upon receiving the loopback
request, the Remote Unit would loop only the traffic for that T1 back onto the OC-3
toward the Local Unit. The Local Unit can then send and receive test patterns for that
T1. The Local Unit would send the pattern onto the OC-3, the Remote Unit would loop
the traffic back toward the Local Unit, and the Local Unit would monitor the traffic for
errors. To verify the circuit, a technician can have the Local Unit inject errors into the
test pattern and verify the errors are received. And, with remote management, this
entire test can be done from the Central Office location or a management station on the
same network as the Local MM840 Unit.
Page 2 of 3 10/4/2005

Fort Bragg: Point-to-Point T1 Delivery
Mini-Mux 840 Lite
Central Office
Remote Location
Voice
Switch
T1s
MM840L
OC-3
1+1 APS
MM840L
T1s
DMX
Mini-Mux 840 Lite
Only 1 RU (1.75”) of rack space
Minimal power consumption (typically less than 30 Watts)
SONET DCC allows management of both MM840L from the Central
Office.
Flexible remote management options, including a Web Browser interface
Integrated testing features such as loopbacks and T1 test pattern
generator/receiver
Figure 2 – Mini-Mux 840L for delivery of T1 circuits
Yet another key advantage is the remote management. The Local and Remote units
communicate using a 192 kbps SONET DCC (Data Communications Channel). The
MM840L has an integrated Web Browser interface. From any computer on the same
network as the Local Unit, a technician can open a web browser (Internet Explorer,
Netscape, etc.) and enter the IP address for either the Local Unit or the Remote Unit.
An intuitive graphical web browser interface allows for monitoring and management of
the MM840L. This allows technician(s) to monitor for alarms, turn up circuits, and
troubleshoot using the loopback and BERT functions on either or both MM840L units.
Further Information:
Further information on Charles Industries products may be found at:
http://www.charlesindustries.com
For further information on this application, please contact:
Jeff Warren
Systems Engineer
Charles Industries
847 258-8470
mailto:jwarren@charlesindustries.com?subject=App note question
Page 3 of 3 10/4/2005