ADTRAN DE-4E - Manual (Page 17)

A-1 Section 61245207L2-5, Issue 3 61245207L2-5C
Appendix A
FT1 Loopbacks
GENERAL
This Appendix is an overall reference to the loopback
capabilities of the ADTRAN Fractional T1 system.
Included in this Appendix is a description of the FT1
loopbacks and the methods for activating the FT1
loopbacks.
FT1 LOOPBACKS
Figure A-1 shows the application from the central
office (CO) to customer premises. The FT1 Repeaters
are shown for convenience and are not necessary parts
of the FT1 network. The loopbacks shown are as
follows:
A. FT1 DP network loopback
B. FT1 DP CPE loopback
C. FT1 Repeater # 1 network loopback
D. FT1 Repeater # 2 network loopback
E. FNID network loopback
F. FNID CPE loopback
There are two loopbacks available to the FT1 DP.
The FT1 DP network loopback loops the FT1 signal
back to the network. The FT1 DP CPE loopback
loops the FT1 signal back to the customer.
The FT1 DP network loopback is a digital loopback
toward the CO (see Figure A-2). This loopback is
initiated by the OCU latching loopback command
(N1010101), or by the craft interface, when available.
The OCU latching loopback code is detected in the
primary DS0 of the FT1 circuit (the channel where the
FT1 DP is physically installed) to control the FT1
circuit looping. When the FT1 circuit is looped, all
DS0s in use will be looped back toward the network.
The DS0s will be transmitted on to the customer.
The FT1 DP CPE loopback is a digital loopback
toward customer premises as shown in Figure A-3.
This loopback is initiated by the REM LBK button on
the FNID, or by the craft interface when available.
When the FT1 circuit is looped, all DS0s in use will
be looped back toward the customer. All DS0s in use
will be filled with all 1s and sent toward the network.
Figure A-2. FT1 DP Network Loopback
DSX-1
Interface
Central Office
FT1 DP
D4
Channel Bank
FNID
HDSL
Local Loop
DS1
Interface
Customer Premises
Figure A-3. FT1 DP CPE Loopback
DSX-1
Interface
Central Office
FT1 DP
D4
Channel Bank
FNID
HDSL
Local Loop
DS1
Interface
Customer Premises
Figure A-1. FT1 Loopbacks
DSX-1
Interface
Central Office
Customer
Premises
Equipment
FT1 DP
D4
Channel Bank
FNID
T1 NIU
A B E F C
FT1
Repeater
D
FT1
Repeater
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