User manual

Wide Bank 28 DS3 - Release 2.4 July 2004 2-31
Product Description
Tests and Loopbacks
Low-Speed Metallic Loopback
The low-speed metallic loopback loops the received low-speed signal back to the low-speed
transmit using a relay. This Carrier Access Corporation-unique loopback provides “point-of-
entry” fault-isolation between the Wide Bank and attached DS1 or E1 equipment to detect DS1
or E1 line problems.
A spare low-speed card is required to provide metallic loopbacks toward the low-speed
connections. The metallic loopback function may not be available if the spare low-speed
channels are in use. If this is the case, the Wide Bank will not execute a metallic loopback on
the low-speed channel requested. Also, only four low-speed channels (in different spare
groups) can be selected for metallic loopback at one time.
Figure 2-13 Low-Speed Metallic Loopback Mode
C-bit FEAC Loopback Code Word Detection
When the Wide Bank is configured for C-bit framing mode, the DS3 monitors and detects low-
speed loopback requests sent over the C-bit far-end alarm and control signal. When a low-speed
loopback code word is received an equipment loopback is activated (see Low-Speed Equipment
Loopback Mode on page 2-30).
NIU Loopcode Detection
Each low-speed circuit on the Wide Bank can monitor and detect Network Interface Unit (NIU)
loopback codes originating from the DS3 network. A standard 5 second integration time to declare
loop-up or loop-down codes is used. Upon detecting an NIU loop-up code on a DS1 or E1 channel
of the DS3, a low-speed equipment loopback will be executed by the Wide Bank for that channel.
This provides for standard loop testing from the DS3 end, as if a physical DS1 or E1 NIU (“Smart
Jack”) was connected to each of the 28 DS1s or each of the 21 E1s.
Send AIS
Relays
Trans-
ceiver
Selector
M13
Framer
Trans-
ceiver
Relays
Spare LS Card
HS Card
Toward DS3
Looback
Relays
Trans-
ceiver
LS Card
Toward DS1/E1
DS1/E1 DS3