68P80801E30-A 5/1/2002
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Gen 3 Site Controller System Manual
Chapter 6 System Testing
Remotely Looping Back the T1 Site Controller for BER Testing
Three Different Ways to Start and Stop a T1 Line
Loop-Back on the Site Controller
Inband Line Loop-Back
A craftsperson inserts a T1 test set into the line going to the site controller.
The test box then sends a loop-up code, consisting of a repeating
00001
pattern, across the entire T1 frame. All 24 DS0s have the data pattern across
them. The site controller detects this pattern and enters loop-back mode.
When the craftsperson is done testing the T1 line, he sends the inband loop-
down code to the site controller. This code is a repeating
001
pattern across
the entire T1 frame. The site controller detects this pattern and quits looping
the T1. Normal operation on the T1 line can now begin.
Front Panel Line Loop-Back Switch
The front panel of the site controller includes a Loop-Back Switch.
Depressing the SEL/LOOP button for more than two seconds causes site
controller to enter line loop-back mode. Depressing the SEL/LOOP button
for two seconds again deactivates the line loop-back.
Line Loop-Back from a ANSI T1.403 Loop-Back
Command on The Facility Data Link
A craftsperson uses a T1 test set and inserts it into the line going to the site
controller. The test box then sends a T1.403, line loop-up, bit-oriented
message on the FDL towards the site controller.
When the craftsperson is done testing the T1 line, he sends a T1.403, line
loop-down, bit-oriented message on the FDL towards the site controller.
The T1.403, line loop-up and down commands transmit on the T1 Extended
Super Frame Facility Data Link. The loop-up, bit-oriented message is
00001110 11111111,
with the rightmost bit transmitted first. The
loop-down, bit-oriented message is
00111000 11111111,
with the
rightmost bit transmitted first.
How Payload Loop-Back Works on the Site Controller
A craftsperson inserts a T1 test set into the line to the site controller. The test
box then sends a T1.403, payload loop-up, bit-oriented message on the FDL
towards the site controller.
When the craftsperson is done testing the T1 line, he sends a T1.403,
payload loop-down, bit-oriented message on the FDL towards the site
controller. Normal operation on the T1 line can now begin.