atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's Adtran TDU 120e - Fax problem

Hello, I am using a point to point T-1 between two sites w/ an Adtran TDU 120e at each site. We are splitting the T-1 (12/12) for data/voice. But ever since I have installed it I am having a little trouble with fax calls not working. Some fax's go thru but then sometimes I get a "Bad Line Condition" error. Any help would be great.

P.S. the fax is a analog port on my Siemens Hipath 3000 PBX. The Siemens people say itr is not thier equipment.

I have seen this happen before on other systems. It was due to slips on the circuit and we were able to get the circuit provider to correct the situation. Usually, slips don't affect voice traffic because they can't be detected by the human ear. Data (fax) traffic is much more sensitive to slips.

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Ed
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How come there's always enough time to go back and fix it a second time?

Is there a way to see if I am having slips?

I am pretty sure that the Adtran TSU120e will give you a display on the error log. I can't tell you how to get there, but I am confident that Adtran's manual has the information you will need. If all else fails, their techncal support is awesome.

The unit keeps a cumulative total of slips, and if it's just a few, say less than a hundred, then I doubt that is your problem. If it's up in the 4-5 digit range, I think you can figure out the rest!

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Ed
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How come there's always enough time to go back and fix it a second time?

Need a little more info on what equipment is hanging off each end of the point to point T1 line. Assuming that there is a PBX at each end, how are you connected to the switched public network? T1 DID/DOD service, T1-PRI, or only via analog trunks.

If your inter-PBX T1 is suffering from timing slips knowing the above is essential in resolving your trouble. First, a point to point (Pre-Prem) T1 does not derive T1 clock from the network. I have heard this argument from customers before, however if a Telco, or any other service provider, T1 does not terminate in a network providers switch, T1 multiplexer (Such as a D channel bank, or 1/0 DCS frame, AKA: DACS) then no network service provided timing is introduced by the provider. Timingis sole the customers. Knowing how your PBX's are timed is important to avoid timing slips between the PBX's, and the chnace of a timing loop, where no clock timing is present.

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Field Ops is right,

Depending on who is providing the clocking for this circuit? If it's a PTP circuit, you need to provide clocking (timing), i.e. the host site should be set for DSX timing and the remote for NI.