Specifications

Section 520-10S-WI3-203
030-101591 Rev. B
R
14
0806I3RB
47
41
13
7
5
15
55
49
Figure 14. Single Loopback Operation Diagram − Line Repeater Mode
DSX-1
Fiber Multiplexer
NET
(DSX)
CPE
(SPAN)
47
41
13
7
5
15
55
49
520-10SWI3
(as Line Rptr)
AIS
NET
(SPAN)
47
41
13
7
5
15
55
49
Figure 15. Dual Loopback Operation Diagram − Line Repeater Mode
520-10SWI3
(as Line Rptr)
CPE
(SPAN)
47
41
13
7
5
15
55
49
DSX-1
Fiber Multiplexer
NET
(DSX)
NET
(SPAN)
5.3 Remote Loopback (Line Repeater Mode)
When configured as a line repeater, and loopback is activated
from the Network side (single loopback), the unit loops the sig-
nal received from the Network on Side 1 back to the Network
on Side 2. At the same time, AIS is sent toward the CPE. The
loopback path is provided with signal regeneration. Refer to
Figure 14.
In the dual loopback mode (i.e., looping back both the Network
and CPE side of the unit), the unit loops the signal received from
the Network on Side 1 back to the Network on Side 2 and loops
the signal received from the CPE on Side 2 back to the CPE on
Side 1. Both loopback paths are provided with signal regenera-
tion. Refer to Figure 15.
5.3.1 Remote Loopback − Arming
When configured as a Line Repeater, and before loopback can
be activated, the unit must be armed. This is accomplished by
sending the NIU loop-up code 11000 from the distant end (SSC
or Digital Test location) for a minimum of five seconds or four
consecutive patterns of the 16-bit ESF DataLink code 0001
0010 1111 1111 for a minimum of 16ms.
Upon receiving the appropriate inband code for the specified
time frame, the front-panel LPBK LED begins flashing at 1-sec-
ond intervals.
- NOTE -
The Arming condition remains in effect for a period of 120 minutes.
If no action is taken during this 120-minute time frame, the unit times
out and returns to normal operation.
5.3.2 Remote Loopback Activation
When the unit is armed, actual loopback activation is then ac-
complished by sending the 16-bit inband code 1100 1010 1111
0001 (CAF1 HEX) for a minimum of five seconds to the Side
1 transmission path.
After receiving the code for the specified time frame, the front-
panel LPBK LED illuminates and the 120-minute Loopback
Timeout feature (if enabled) is activated. At the same time, AIS
is sent toward the CPE. After the 120-minute time frame, loop-
back automatically releases and the unit returns to normal
operation.
- NOTE -
If the 120-minute Loopback Timeout feature is not enabled,
loopback remains in effect until the front-panel MLB button is
pressed or until the loop-down code is received.
5.3.3 Remote Dual Loopback Activation
Before the dual loopback can be activated, the unit must first
be put into the single loopback mode (see paragraphs 5.3.1
through 5.3.2). Once single loopback is established, dual loop-
back is accomplished by sending the 16-bit inband code 1100
1010 1111 0010 (CAF2 HEX) for a minimum of five seconds to
the Side 1 transmission path.
- NOTE -
16-bit inband code can be sent in either unframed, SF or ESF formats.
After receiving this 16-bit inband code for the specified time
frame, the front-panel LPBK LED begins flashing and the
120-minute Loopback Timeout feature (if enabled) is acti-