5-14
MAX Administration Guide
Administering E1 and T1 Services
Using line diagnostics
event register of the MAX 3000 unit’s drop-and-insert Line 3. However, the Clr ErrN
commands do not clear the performance registers for the line. The Clr PerfN command clears
all performance registers for Line N, restarts the current time period, and begins accumulating
new performance data.
Note:
Error events have no meaning for D4-framed lines. A D4 line uses the Superframe
format to frame data at the physical layer. This format consists of 12 consecutive frames
separated from one another by framing bits.
Initiating a line loopback test
Note:
Do not activate a line loopback test when a call is active on the line because the test
disrupts data flow between the codecs connected to either end of the network line.
Line LB1 is a Line LoopBack (LLB) command for Line 1 in a T1 slot, Line LB2 is a Line
LoopBack command for Line 2 in a T1 slot, and so on. When you start the line loopback test
for a T1 line, a remote device can test the T1 line and the MAX unit’s interface to the T1 line.
All signals received by the MAX unit are looped back toward the remote unit. The remote unit
can determine the quality of the T1 line by comparing the sent signal to the received signal.
The LLB occurs behind the unit’s Channel Service Unit (CSU) repeater, which boosts the
signal on a T1 line, or Digital System Cross-connect (DSX) signal-conditioning module, which
amplifies signals. Drop-and-Insert channels, which enable a single T1 line to carry both data
and voice traffic, are also looped back.
Note:
Do not activate LLB when a call is active on the line; doing so disrupts the data flow
between the codecs connected to either end of the network line.
The unit responds to both the inband LLB signal and the Facility Data Link (FDL) LLB
message. A management device can put the unit into LLB. A management device is a unit, on
a T1 line, that measures the line’s performance and can send management signals to other
devices on the line.
To initiate a loopback test on the first T1 line, highlight Line LB1 and press Enter. After
prompting for confirmation, the unit starts the loopback test and the Alarm LED lights up.
When you exit the menu option, the unit automatically deactivates the loopback.
Swapping NFAS status
The Switched D Chan parameter, in the Line Diag menu, swaps the status of the primary and
secondary Non-Facility Associated Signaling (NFAS) Dchannels. It applies only to T1 lines
using NFAS signaling.
NFAS is a form of out-of-band signaling that maximizes the number of PRI lines supported by
the signaling of one external Dchannel. NFAS is a special case of ISDN signaling in which two
or more T1 lines use the same D-channel, and add a backup Dchannel. NFAS is required for
the Switched-1536 data service. Because all 24 channels of the T1 line carry user data, the
Dchannel must be on another line.