Table E. Alternating Loopback Activation Sequence; Table F. Latching Loopback Activation Sequence - ADTRAN T400 DDST III Installation And Maintenance Manual
Local power digital data station termination w/local power
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Also See for T400 DDST III:
- Installation and maintenance manual (9 pages) ,
- Installation instructions (4 pages) ,
- Installation & maintenance (3 pages)
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Terminating CSU Latching Loopback to DDST III or
DSU/CSU
•
From a test system or set, send a CSU Latching
Loopback Disable command (35 TIP bytes); see
subsection Network Interface Equipment Latching
Loopback .
Manual Loopback
Manual loopback is activated from the faceplate of the
DDST III by pressing the LOOPBACK ON/OFF (SW1)
button. Manual loopback will automatically terminate
after 20 minutes unless otherwise terminated by pressing
the button again or by receiving a Latching Loopback
Disable command from the CO.
To activate Manual Loopback
•
Press the LOOPBACK ON/OFF button; the ACTIVE
LED turns On .
To deactivate Manual Loopback
•
Press the LOOPBACK ON/OFF button; the ACTIVE
LED turns Off , or
•
Wait for the 20-minute time out, or
•
Receive a Latching Loopback Disable command
from the CO.
Network Interface Equipment Latching Loopback
Because some remote test systems do not support a
Repeater loopback for rates other than 56 kbps, the NIE
latching loopback method can be used to loop the DDST
III at all other rates. This loopback test may require
programming of the loopback select code or the complete
sequence into the test system.
Alternating and latching loopback sequences are
described in Tables E and Table F. The All-1s Repeater
Release code is described in Table D.
Table E. Alternating Loopback Activation
Sequence
Function
Activate loopback
Maintain loopback and
test for bit errors
Clear loopback
* - Don't Care bit D - data bit
61212.021L3-5C
Received Bytes
Four consecutive bytes of
specified loopback code
*0101010 - OCU
*0101000 - CSU
*0101100 - DSU
Data byte alternating with
loopback code
example:
*DDDDDD1/*0101010
Four consecutive data bytes
without CSU loopback code
Section 61212021L3-5, Issue 3
Table F. Latching Loopback Activation
Sequence
Function
Byte Code
Clear existing
Transition in
loopbacks
progress (TIP)
*0111010
Identify device
Loopback select
to be looped
code (LSC)
*1010101 - OCU
*0110001 - CSU
*1000001 - NIE
Prepare
Loopback
to loop;
Enable (LBE)
send MAP
*1010110
code after
30 bytes
Activate
Far-End Voice
loopback
(FEV)
*1011010
Minimum of 35 TIP bytes required to disable established
latching loopback.
* - Don't Care bit
# of Received
Bytes
Minimum of 35
TIP bytes
Minimum of 35
LSC bytes
Minimum of 100
LBE bytes
Minimum of 32
FEV bytes
5
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