Hey Folks, Hoping to get some insight into this problem I had with an Adtran HDSL circuit. The sucker has got a new doubler, new smartjack, and no apparent cable issues. Not even any bridge tap (I NC'ed it to cable and the cable tech found it had already been cut off). Anywho.....it always passes QRSS yet it will fail 1 in 8, all0's and all1's. BUT it seems to pass one of these 3 patterns, then fails the next intermittently.I gave up and patched to the spare. I'm new to specials (4 months) but I've never seen this before....any ideas?
All 1's will stress-test a repeater. So it could be bad if you get failures with it.
QRSS isn't a very stressful pattern like the other ones are, so seeing no errors when testing with it isn't unusual.
Failing All 0's and/or 2^20 could indicate something is optioned AMI rather than B8ZS.
like I said, new doubler, new smartjack. Could it be the office repeater, even though it test ok?
You said you patched to a spare. Is it good on the patch? If so something in your original circuit is bad.
Like Dex said failing all 1's indicates a bad repeater. The only thing all zero's should be used for is confirming B8ZS. Change the repeater and test again.
I don't know what the 1:8 pattern is for.
QRSS was used to simulate real T-1 traffic and was low stress as Dex pointed out.
Where's it failing at...r-card, doubler, or c-card? Not sure how your circuit is designed but get a tester, or if you have test access, start by looping the c-card from the dacs or closest dsx, and stress test the circuit with pattern T1 Daily or 55 Octet. If it passes, loop the doubler and if that passes go for the r-card. This should give you an idea about what section of the span is bad.
Also use the PM data. The Adtran cards pretty much record everything and if you can decipher the info it will give you a clue as to where to look. If it is a model that has the Tscan feature it should have a bad slice detector under the troubleshooting menu... it will give you the distance to the bad splice. Sometimes it is right on, other times you need to give or take a few hundred feet.
We used QRSS to stress test the PHYSICAL portion of the job (jacks, cable connections, patch cords, etc.). All '1's verifies that the circuit will pass AMI and as Dex and Bill said should stress the repeater and all '0's is used to prove B8ZS.
1 in 8, 3 in 24, 2-20 are all miscellaneous stress tests. It sounds to me like the circuit has some of it's repeaters or circuit boards wired wrong. Maybe some parts wired for AMI and others for B8ZS, maybe the LBO is wrong.
You're going to have to break the circuit down into pieces and check each part. Use standard troubleshooting techniques- go to the midpoint of the circuit and test back to the source. If that works/fails then keep going to the next midpoint till you find the bad segment.
ANY circuit should pass all '1's. If it won't pass that don't bother with anything else till you can get that part working.
Sam
I think that the "all 1's stresses a repeater" rule only applies to a real T1 span using 239 style repeaters (which were essentially analog dc op-amps). The OP said it is provisioned over HDSL, which is completely different - all 1's produces a signal on the span that is really no different electrically than any other data stream.
Just my 2 cents... [sorry, haven't run my jaw in a while]
Jim
**************************************************
From a bunker in the hills of Pennsylvania
When swapping out parts were you able to switch shelf/slot positions in the C.O; repeater housing and cust-prem housing? Backplanes and breakout wiring can do be failing too.
The most important thing to remember when troubleshooting an HDSL2/4 facility is that it is an analog transport facility for the digital DS1 payload. Hence the TC-PAM line encoding. BERT testing with traditional digital stress patterns will help isolate trouble to the circuit packs(HLU,HRU,HRE)themselves or to equipment or wiring on either side of the HDSL span, but it will not just cause errors on the HDSL facility because you send different patterns of 1's & 0's. If you are infact working with Adtran HDSL4 technology on this trouble their should be a wealth of PM Data info on the facility to help you troubleshoot. SNR margins & Attenuation between the network elements on the span, splice detector/histogram, facility and alarm history, DSX-1 and DS1 performance data, and HDSL span performance data(ES,SES,UAS)can all be used to help isolate the trouble without actually taking the circuit down
If you are a Special Services technician with an ILEC you should have access to a remote testing system that you can use to retrieve all pm/provisioning/alarm info off of the Adtran HDSL4 facility thru the Facility Data Link/T-SCAN feature built into the HDSL electronics.
once again, it's not an H4 circuit, it's an Adtran HDSL 4 wire circuit. No Tscan. The 1rst adtran hdsl technology. The end smartjack is called an HTUR. I could swap to H4 technology but the CO has no spare office repeaters, atleast they didnt 2 weeks ago. I've since had the Spare converted to be the main. Now the circuit that was giving me problems is a spare I need to fix, but my tech log has about 20 non-measured tickets I need to get to when I get time (HAHAHAHA Spare time...WTF is that???)
You need to have the testing tech segment the circuit. Testing the whole path end to end will not tell what item is causing the trouble. I'm betting there is a bad low speed card or DCS in the path. QRSS will usually ID bad cable. Since QRSS passes I'm betting on electronics as the culprit.
1:7 (also written as 1-in-8) – An 8-bit pattern that contains a single one and is used primarily to
test clock recovery and may be used framed or unframed. When transmitted unframed the pattern
has a maximum of seven zeros, and the pattern will not force the B8ZS line code. When
transmitted framed, framing bits can force the maximum number of consecutive zeros to eight,
and the pattern will invoke the B8ZS code in interfaces optioned for B8ZS
ALL ONES – An unframed pattern that has ones in all payload bit and frame bit positions. It
causes transmitter circuitry to consume the maximum possible power. In a T1-Carrier span with
line- powered repeaters, this pattern will verify that the dc power is regulated correctly. An All-
Ones pattern is the same as an Alarm Indication Signal (AIS) or “Blue Alarm,†which is sent
forward by an interface that has lost its input signal. It will never invoke the B8ZS line code.
This pattern only should be used in isolated segments of a transmission system and not in
transmission chains; otherwise, it may produce unpredictable results.
ALL ZEROS – A framed pattern having all payload (non-framing) bit positions set to zero. The
pattern is used to verify that all interfaces in a transmission chain are optioned for B8ZS. If any
interface in the chain is incorrectly optioned for AMI, it will fail immediately because no pulses
are available for clock recovery.
Originally posted by phoneman69:
I could swap to H4 technology but the CO has no spare office repeaters, atleast they didnt 2 weeks ago.
Which Telco do ya work for? With that part of AR there's a 50/50 shot your "no spare card issue" can be cleared up right here.
... PM me if you don't feel comfortable stating your employer here in an open forum.
AS for the patterns that fail, its not my choice. It's the Full Maintenance NI test that we as outside techs must use to close out a trouble report. Its consist of 5 min qrss, like 2-3 min 1n8, 2 min all 1's and 2 min all 0's....as far as what telco I work for, lets just say it's probably the biggest in America.....
The first generation of Adtran HDSL was a big improvement over conventional DSX1 spans but the older technology can get a little flakey at time… Since you
from within the bowls of the death star, I can’t directly help ya, but here’s what I’d do
Your SSC tester should be able to turn in a ticket (TFAS?) to your CPC requesting a redesign from the first generation HDSL to HDSL4. Doing it on an internal order (aka bureau CLO or aka B-CLO) should generate a PICS ticket to send new cards to the C.O. you’re working out of. I’m sure things have changed since I was there, I know the TFAS process has come along since I left their CPC.
Once again???....Your original post didn't specify whether you were working on legacy 2B1Q 4-wire HDSL or HDSL4, only that it had a doubler/range extender in the route, which meant it had to be a 4-wire technology. The Adtran HDSL technology registers a lot of pm data on the HDSL span & DS1 payload inbound on either side of the HDSL carrier. You haven't posted any of that information. Also, is this circuit working directly off of a repeater shelf in the serving CO straight to the cable pairs or is it working off a multiplexer at a remote terminal in the field??....You haven't posted enough info on the circuit build/design for anybody here to help you. Everybody FYI!!!...CART(craft-access-to-remote-testing)is the semi-automatic test application he is using. It is integrated with ATAS(Automated-Testing-and-Analysis-System)to provide remote field testing
The CART full maintenance ni test he mentioned initiates an automated test sequence thru the ATAS system and loops & runs QRSS,1 in 8,all 1's & all 0's to the Network Interface Unit chosen(A-end or Z-end of the circuit)at the start of the test from the closest digital test point(DTAU,DACS,etc.)to the niu being tested. A single bit-error on any pattern during the test will cause the entire test to fail
Another tidbit of info for everybody on this post. Running the all 0's test pattern for any longer than a few seconds on DS1 circuits is a complete waste of time. The all 0's pattern does not produce any pulses in the bitstream and is only used to verify that B8ZS encoding is being invoked on network elements, equipment & CPE
phoneman69 send me an e-mail with any questions.
I believe I have said before that it is a 4-wire hdsl circuit from adtran, no its not an hdsl4. It runs off a repeater shelf in the co straight to the cable prs. Then it hits a doubler, a xbox, then the smartjack. It is the old gray-faced hdsl technology. Why does my company still use it when they could use HDSL4? Probably cost less $$ and we all know the CEO was once an accountant.....
I have since had a few more circuits of this same design give me the same problems. I am starting to think that the old Adtran HDSL technology has outlived it's usefulness. Never have this problem with HDSL4 or even HDSL2.
Ok then. Order the HDSL4 HLU & HRE4 u need from FSL/PICS and show usage to an RT-CLLI. When the plugs arrive at your workcenter, drive down to the CO and slot the new HLU and then go to the field apparatus case and change the Doubler/HRE out and then go to customer premise and change HRU for HRU4. After circuit is back up, either build a TFAS ticket or have your local DPC(DS1+ circuit engineer) update the span design with the new electronics and send it to the CPG(circuit provisiong group) or CSDC(Customer service design center) whichever is in your region to have the WORD Doc reisssued to reflect the changes
FYI...Adtran's legacy 2B1Q HDSL equipment now looks and operates just like it's HDSL2/HDSL4 stuff. Yes, I know what kind of cards you are referring to and I would absolutely have the entire circuit path upgraded before anymore troubleshooting takes place
Hi gentlemen,
I am brand new to this forum and boy am I glad I found it, the wife is not much help when I come home from one of those 2am call-outs and I am still scratching my head trying to figure out why a T-1 went down and there seems to be no physical reason for it. (lol)
To get on with my comment I feel for phoneman69, I have struggled with T-1 issues lots of times in my 10 year tech history and have been to schools on these pesky circuits but, nothing in the lab works like the real world.
Is there any definite pattern to tell you your dealing with a cable issue or an electronic issue, I know QRSS pattern failure is likely cable issues but are there any other pattern failures more likely to be one or the other?
Hdman66,
to the board. At the top of each Category you'll see a "Post New Topic", that would be the best thing to do. We encourage keeping topics on topic as it helps others in the future with searches to find things. I'm sure you'll get some good suggestions.