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LOOPBACK INFORMATION
External Coax DS3 Loopbacks
Two types of External Coax DS3 loopbacks can be
used to isolate trouble and verify proper DS3 data
path operation. For accurate isolation, this type of
loopback is preferred over the menu selected loop-
backs since it checks the entire signal path and
isolates the equipment at each end. An external coax
loopback cannot reliably be done if the total length of
coax exceeds 900 feet. Both of these types of loopback
disrupt normal traffic on the coax.
■ An External Coax DS3 Local Loopback can be per-
formed to verify proper DS3 Mux data operation by
looping the DS3 transmit output to the DS3 receive
input either locally with a short coax or at the DS3
cross-connect. The Line Build Out option should be
set to Short for a total coax length of 0-225 feet and
Long for 226-900 feet. The clock source must be local
for a coaxial loopback. Verify that the STATUS LED
turns green after about ten seconds. The Status menu
should show that the DS3 TX and RX Status is
NORMAL. Also, zero errors should be seen in the first
15-minute column of the DS3 Qrtr-Hourly report
under the Performance Monitoring menu. Select
“Reset Performance Registers” if necessary to clear
previously reported errors.
■ AnExternal Coax DS3 Line Loopback can be
performed to verify proper far end equipment DS3
data operation by looping the DS3 transmit coax from
the far-end to the receive coax, either locally near the
Total Access shelf or at the DS3 cross-connect. The
far-end clock source must be local for a coaxial
loopback. The far-end equipment Line Build Out
option must be set for the length of coax present. The
far-end equipment must be checked for receive DS3
signal status and no errors.
Menu Selected DS3 Loopbacks
■ AMux Menu Selected DS3 Line Loopback can be
used to verify that the far-end equipment can talk to
itself over the entire length of coax with the On-line
Mux receiving and then re-transmitting the same
data. All loopbacks will disrupt any normal traffic on
the coax. The DS3 receive line interface unit per-
forms this loopback. It performs receive clock and
data recovery and B3ZS decoding/encoding before
re-transmitting the data.
■ AMux Menu Selected DS3 Local Loopbackshould
not be used to verify the DS3 data path since it does
not test the entire DS3 data path. A Local Loopback
should be used only to internally loopback the DS3
signal on the Mux to verify Access card T2, E1, T1 data
paths.
DS3 MUX TROUBLESHOOTING
TROUBLESHOOTING INFORMATION
1. POWER LED ON RED continuously.
■ Equipment fault.
1. Momentarily unseat and then reseat the Mux to clear LED.
2. Replace Mux if trouble persists.
2. POWER LED OFF and POWER LEDs of all other cards in shelf are ON.
■ -48V fuse on Mux is blown.
1. Replace the Mux. Fuse is not field replacable.
3. Power LED is ON YELLOW,Status LED is OFF and Mux does not pass traffic.
■ Mux is provisioned for OOS-Unassigned.
1. Provision Mux to be In Service.
4. No alarms are on in Mux and it does not pass traffic.
■ The DS3 channels are not mapped to access card slots.
1. Provision each channel to the desired slot.
5. LEDs do not turn ON when pushing Test/Enable button.
■ There is an equipment fault.
1. If Mux is still On-line, force switch to the other Mux.
2. Momentarily unseat and reseat the Mux to clear trouble.
3. Replace Mux if trouble persists.
6. STATUS LED is ON in Mux A and B and Status menu shows DS3 RX LOS.
■ DS3 receive signal is not present.
1. Check for correct RX coax connection. Ensure TX and RX coaxes are not
reversed.
2. Check for faulty coax or coax connector.
3. Check far end equipment for proper TX signal. Perform External Coax DS3
Line Loopback.
4. Perform an External Coax DS3 Local Loopback to verify that Mux units and
shelf are OK.
7. STATUS LED is ON RED in Mux A and B and Status menu shows DS3 RX OOF.
■ Receive DS3 signal is present but valid DS3 framing is not being received.
1. Check for correct TX LBO setting on far end equipment.
2. Check far end equipment for proper TX signal. Perform External Coax DS3
Line Loopback.
3. Perform an External Coax DS3 Local Loopback to verify that Mux units and
shelf are OK.
4. Ensure framing format for both units is the same.
■ Check to ensure the clock source is not identical at both ends (i.e., both
ends set to Local or both ends set to Loop).
8. STATUS LED is ON RED in one Mux only, OR,No alarm LEDs on in either Mux
but receive DS3 PM errors occur on one Mux.
■ Faulty Mux DS3 receiver.
1. If this Mux is still On-line, force a protection switch to the other Mux.
2. Momentarily unplug and then plug in Mux to see if trouble clears.
3. Replace Mux if trouble persists.
TROUBLESHOOTING CONT.
9. No alarms are active in either Mux but receive DS3 PM errors occur in
both Mux units.
■ Marginal DS3 receive signal
1. Check for correct TX LBO setting on far end equipment.
■ Total length of coax cable > 900 feet (728A or 734A).
1. Reduce cable length to <
900 feet.
■ AC current is flowing in RX coax shield due to a frame ground
potential difference at ends of cable.
1. Improve grounding or isolate one end of coax shield from frame
ground.
■ Check to ensure the clock source is not identical at both ends (i.e., both
ends set to Local or both ends set to Loop).
10.Status LED is ON YELLOW in one or both Mux units.
■ Marginal DS3 receive signal at far-end equipment.
1. Check for correct TX LBO setting on both Mux units.
■ Far-end’s receive DS3 signal is bad.
1. Force a Mux protection switch. If the trouble clears, the Mux which is
now Off-line has a bad DS3 TX output.
2. Force the now Off-line Mux back On-line and momentarily unseat
and reseat the Mux to see if the trouble clears.
3. Replace Mux if trouble persists.
■ Check to ensure the clock source is not identical at both ends (i.e., both
ends set to Local or both ends set to Loop).
11.DS3 PM errors occurring and/or DS3 status indicates OOF.
■ Wrong clock source.
1. Change clock source to loop if the current clock source is local or
vice-versa.
■ Check to ensure the clock source is not identical at both ends (i.e., both
ends set to Local or both ends set to Loop).
COMPLIANCE CODES
This product is intended to be installed in a Restricted Access Location and in
equipment with a Type “B” or “E” enclosure.
WARRANTY
Warranty for Carrier Networks products manufactured by ADTRAN and
supplied under Buyer’s order for use in the U.S. is ten (10) years. For a
complete copy of ADTRAN’s U.S. Carrier Networks Equipment Warranty:
(877) 457-5007, Document #414.
PRICING AND AVAILABILITY 800.827.0807
TECHNICAL SUPPORT 800.726.8663
RETURN FOR REPAIR 256.963.8722
www.adtran.com
CODE INPUT OUTPUT
Power Code (PC) F C
Telecommunication Code (TC) – –
Installation Code (IC) A –