A strong DS1 pulse transmitted from a service provider NIU toward the CSU/CPE will generally travel quiet a distance on healthy copper. Usually well over 1000ft. Most ILEC's by policy regen the DS1 pulse from the facility side of the NIU and transmit to the customer at 0 to 0.5 -dbsx/6vpp. The only LBO setting I have seen on any NIU/HRU in the last 10years is a transmit LBO toward the CPE/CSU from the NIU with generally 3 to 4 settings: 0 dbsx, -7.5dbsx, -15 dbsx, and -22.5 dbsx. Each LBO setting is referenced with a guesstimated cable footage with the highest usually being 655ft. Those cable footage estimates were based on old/ancient topology and really don't come anywhere close to how far DS1 will travel on CAT3 or CAT5 cabling.
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Software settings & tolerances can vary between CPE/CSU manufacturers also. Typically a DS1 pulse can be recovered/regenerated on a T1 span in the OSP every 3,000 to 6,000ft between repeaters(up to -28.0 -dbsx), depending on cable gauge. I have seen integrated CSU's on PRI equipment that would not achieve DS1 sync with the ILEC's NIU with only -15dbsx atten on the receive pulse, either because that CSU was not designed to accept an overly attenuated DS1 pulse or it was not software set to regen the pulse before converting it to unipolar, or it had no such setting. The CSU can also be incorrectly set to pad(LBO) the DS1 pulse toward the providers NIU. I have seen many tech's on both sides of the fence incorrectly set LBO based on cable footage between NIU's & CSU's not realizing that what they were doing was causing the problem.
Not having the proper test equipment is a problem when it comes to DS1/T1. I would not be comfortable extending a DS1 across house cable,iw, etc. without having a good copper analyzer(Fluke,Sidekick,Dynatel) & a T-BERD or it's equivalent handy. The Fluke & Dynatel sets are usually optioned for wideband capabilities & you can do single ended testing with there respective far-end devices. Widebanding the copper pair at 772Khz(center freq. of baseband bipolar DS1) will give you pretty much the exact amount of attenuation you can expect on the DS1 pulse between devices.
Glad to see this post. Here is a scenario that I have for a customer who often looses his T1 lines at random intervals, although the restoration process sometime takes days. They have two T1 circuits, one is for a PRI and the other for their internet access. They have a number of POTS lines, just so their calls can be forwarded to them when the PRI T1 goes down. the T1's are from AT&T and transported by Verizon, albeit the old GTE territory before the acquisition by VZ sometime back
There is a 24/25 pair cable which feeds from the DMARC to the EU server Room T1 CKTID: 23.HCGS.XXXXXX (Data) SMJK Shelf 1, Slot 6 is located on pairs 16 and 25 of the 25 pair cable T1 CKTID: 23.HCGS.ZZZZZZ (PRI) SMJK Shelf 1, Slot 2 is located on pairs 13 and 23 of the 25 pair cable. The other working pairs are as follows: POTS is working on pair 1 POTS is working on pair 2 POTS is working on pair 3 POTS is working on pair 4 Nothing is working on pair 5 DSL is working on pair 6 POTS is working on pair 7 POTS is working on pair 8 POTS is working on pair 9 POTS is working on pair 10 All other pairs in this cable are spare, non working The approximate distance from the DMARC to the EU server room as measured by a TDR 1s 326' (Opens test) The approximate distance from the DMARC to the EU server room as measured by a 965 Dynatel is 376' (again an opens test) Random vacant pairs were selected to test for metallic faults with the two above mentioned test sets as well as with a Sidekick test set. Pairs 11, 12, 14, 15, 17, 18, 19, 22 and 24 were tested and showed no apparent physical faults. A Strap was placed on pair 17, which should have shown a SC (short circuit) Fault at approximately 336 - 376' +/-. The actual DTF (distance to fault) was measured as 642' with the Dynatel A Fault locate test shows a Strap to fault reading of -333' and the DTF of 654' on pair 17 (Dynatel) Placing straps on pairs 12, 14, 22 and 24 give a reading of 791' each with the TDR -s/b 326' STF Pair 18 shows and DTF of 321', DTF of 46' and STF of 274 ' The faults are rather light but noticeable..
The apparent problem is that the 2 T1 circuits which are in the 25 pair cable are causing interference with each other, possibly the DSL service (or vice versa) and the vacant pairs due to the phenomenon known as signal coupling.
My recommendation to this customer is that the T1 circuits be placed in an Individually Shielded Twisted Pair (ISTP) 22AWG T1 cable. I plan to terminate the new wiring on RJ48C jacks at the DMARC end and RJ48X jacks at the EU end. I try to stay away from terminating IW in 8P8C pugs whenever I can avoid it - been on too many trouble calls where the IW cabling had pulled loose from the 8P8C contacts.
Silver Sam recommends testing the cabling with a T-BERD and I can do that, although I don't know if I can run a 24 hour test with the QRSS pattern for the two new cables. If I can, it would mean a return trip to the EU's premises Of course, I can just build that return trip cost into my proposal, can't I?........if they would accept that, that is.
Is there anything that you think I have overlooked or do you have any other recommendations for me?
Originally posted by zapatogrande: I have for a customer who often looses his T1 lines at random intervals, although the restoration process sometime takes days.
There is a 24/25 pair cable which feeds from the DMARC to the EU server Room
My recommendation to this customer is that the T1 circuits be placed in an Individually Shielded Twisted Pair (ISTP) 22AWG T1 cable.
Right off the bat I’m confused... I’m reading this as the failings are on the VZ side of the demarc, yet your resolution suggestion is to re-cable demarc to end-user server room? Am I misreading something?
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Originally posted by zapatogrande: The apparent problem is that the 2 T1 circuits which are in the 25 pair cable are causing interference with each other, possibly the DSL service (or vice versa) and the vacant pairs due to the phenomenon known as signal coupling.
Do you know or make note of what type of cards are in Slot 2 and Slot 6 for the two DS1 circuits? Depending on the technology used to deploy the circuits over copper to your customers premise, there is a possibility of issues there. I’m reluctant to say that will fix your issues but there are technolgies that do not play nice with each other.
