sundance-communications.com/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's Reminder - T1's can't go very far....

We've been chasing down a serious voice quality issue for a month, and yesterday I finally solved it.

Customer has a test 'dialer', which ties to an Avaya switch via a T1 (switch uses it as extensions, not CO). They also have a production 'dialer' connected to the same switch. I'll use the term 'dialer' for now, because it could be used as a dialer, but right now they don't dial with them, they do QA recording through the Avaya switch.

They recently went back to the test system to prepare for a demo to a prospect. Their software sets up a silent monitor through the switch to one of the dialer's extensions. The dialer then begins a recording of the monitoring session. They open the file in Goldwave (one of the few audio programs that can handle Dialogic VOX formats) and the voices are choppy and garbled.
:bang:

Rob -

People assume that because T-1s are 1.5mbs and Cat 5/6/7 is 100/250/1000 mbs then it's OK to use it for Carrier.

This is a common misconception of CGs.

Surprise! The problem is not the bandwidth, it's the "bleedthrough" from Transmit to Receive.

Run them on separate cables (shielded preferably) and it'll work fine.

Sam

True. Also remember that Telcos rarely provide LBO (line build out) to cover a distance from their RJ48X to go more than 166 feet, the default setting. They don't like to do this because they don't want to have to deal with these headaches.

What Sam has described is indicative of bleed through between transmit and receive for sure.

Sam is right-on here. The transmit and receive pairs should be under a separate cable sheath, preferably shielded and grounded to reduce outside inductive influence. While it's possible to get away with a single cable, it's a crap shoot as to whether it will work properly or not.

We did a job for Siemens years ago and they had a tech on-site that would not extend the T-1 unless the cabling contractor ran 2 separate CAT 3 runs! He got his way and i learned that day about this exact issue!

In Rob's tale of woes above... Unless I'm misunderstanding something Telco ain’t involved with this little puzzle right? He’s talkin’ about a T1 port on a piece of CPE to a T1 port on another piece of CPE right? … or did I miss something?

And yeah… It’s advisable for Telco techs to leave the T1 NID set to 0-166ft (default.) Many times the customer equipment being connected will be well within that distance. And honestly when it isn’t, there VERY OFTEN will not be anyone on-site at the time the circuit is installed that would even know where the equipment is GOING to be located. Playing the odds leaving the LBO set to default is the safest way to go.

That's right, this has nothing to do with a telco. The point was that Dialogic cards expect to be sitting right next to the termination points from the telco, not over a hundred feet to the PBX.

The frustrating point was that the last time "we" (my boss) was in their facility, the dialer was in the switch room, so all the while at first, we assumed it was still there... I mean every time the guy called me from the dialer, I heard the background noise I'd expect from a switch room. Except that there is both a switch room and a server room.... And they're both the size of large living rooms. How the production dialer has survived the logic of their IT dept. I don't know....