Carrier Access Wide Bank 28 DS3 Overview page 5

Maintenance Service Option (MSO)
In addition to providing the same circuit failure protection as Standard DS1 and E1 cards, the MSO DS1
and E1 cards can be replaced without interrupting service on other circuits. The TL1 Access Identifiers
clearly distinguish between standard cards and MSO cards.
The MSO circuit card is made up of two separating sections called the MSO Electronics card and the MSO
Relay card. By separating these sections, a customer can replace the failed DS1 or E1 electronic circuits on
the MSO Electronics card while the MSO Relay card automatically maintains the four DS1 (or three E1)
circuits by switching them to the spare card. Once new MSO Electronics are inserted and pass self-test, the
circuits on the spare card are automatically switched back to the home circuits.
With MSO Relay card
installed in chassis, the
MSO Electronics card
can be removed without
interrupting service
Wide Bank 28 DS3 - Release 2.4
System Overview
MSO circuit card assembly,
comprising MSO Electronics
card and MSO Relay card,
replaces standard low-speed
circuit card
3