atcomsystems.ca/forum Forums TDM Business Telephone Systems NEC Telephones & Systems E1 crc problems on 2400ICS

Hi all.
I have an ICS with many DRU-s at remote locations, all connected to the ICS 2400 via E1, using the proper DAIA interface cards. The E1-s are carried to remote sites via fiber multiplexer. This has been installed in the last millenia and have been bullet-proof. However, the multiplexer is now aging and has been discontinued and in this day and age, everything is IP. So I have purchased a set of E1-over-IP devices and having the hardest time making them work. The main problem I run into is at the pbx side, when I connect an E1 into this tdmoip device I get crc errors on the DAIA card in the switch, and the DRU at the remote site can barely maintain sync.
One of these devices can handle 16 E1 ports. I managed to get 2 E1-s hooked up in a stable manner and thus running 2 DRU-s now for 2 weeks without problem. However, when I connect the 3rd E1 on the pbx site, not only do I have crc errors on this E1, it also generates crc errors on the 1st 2 working E1-s.
This tdmoip device has dual 48vdc power supplies, and I noticed that if I unplug one of the power cords, the first 2 E1-s also become flaky. My biggest attention is on some possible grounding problem. The pbx, the equipment rack and the tdmoip device are all grounded properly. The power plug for the tdmoip device has 3 prongs, +, -, and ground and I'm thinking all is grounded properly. But not sure. There are settings on the DAIA card I played with as well: pad settings for wiring length between pbx and tdmoip device, there is a switch to specify if I'm using 24awg x-connect wire for E1 or coax, there is also a switch for some grounding setting. I think I tried all possible combination of all the above discussed settings - to no avail. The manufacturer of the tdmoip device swears they tested it fully before shipping it to me. But for the life of me, I can't go beyond 2 E1-s. My IP connection is gigabit between the 2 sites, with qos configured properly, so I don't have bandwidth problems (2xE1 is only around 5mbps anyways). The manufacturer is now sending me another set to try (I ordered that one with AC power supplies) But I have to wait a week or two before that arrives.
Meanwhile, anybody has any bright ideas?

Okay ... first, how are you getting E-1 service in Florida?

Secondly, in my experience grounding is usually fatal, as opposed to generating CRC errors. CRC usually means some sort of interference, and usually if I clean up the cabling (make sure that there are no funky junctions, and not running voice in parallel with fluorescent lights, etc.) the CRCs will diminish or go away.

Also, usually, CRCs alone will not prevent communications, though a high CRC rate will sometimes cause delay, jitter, or echo. Are you having any issues with Delay, echo, or jitter?

Do you have a voice path at all?

Have you checked that your cross-connects are correct, no crossed pairs, no split pairs, etc.?

I have E1 over my own private fiber network in my campus. There is voice but it's extremely crackly. It's not suitable for faxes and modems over analog phone lines (which I still have) with that noise.

The distance between the crossconnect cable and some fluorescent light is about 4 feet at the closest point. The same cable route was transmitting the E1 fine for the last 10+ years with to my old fiber multiplexers. It's just this new IP multiplexer that's not taking these E1-s easy...

Crackle and hiss have to come in before or after the fiber, so it does sound like bad multiplexors.

It could also be the power supply to the multiplexors. I would check for clean electricity and a good ground.

Also, does the factory offer any troubleshooting support for the multiplexors?

The company offers tech-support: remote login or email advices. At this point it appears that we have exhausted all those options. I have another one of their multiplexer in its way with ac power supplies. I'll give that a try and if I can make that work while the current one remains the way it is, I'll send it back for a replacement.

You are correct: the crackle doesn't get introduced on the fiber, and I'm also suspecting some un-clear electricity entering the flow somewhere. But not being an electrician geek, I'm not sure how to check its correctness. I know that the grounding pin is wires to a grounding bar in the equipment rack.

One of my colleagues in another town always sells phone systems with a "power conditioner" which cleans up dirty power. And if the customer will buy it, he adds a UPS that also helps regulate power.

It's good he does that. Helps to keep the lines clean. Our phone system has it too. It's a full blown professional setup running 2500 ports. However, there might be problem (maybe) with the power feeding the multiplexer. I shall know when I get the next multiplexer.