sundance-communications.com/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's Channel bank FXS channels losing dial tone

Hopefully this is the appropriate forum...

I have this annoying issue affecting channel banks where random fxs channels lose a dial tone. Even if you put the line onhook and offhook multiple times you cannot regain a dial tone unless the channel bank is power cycled. When ever this happens a side tone is still present. I have swapped channel banks with different units of the same make and model as well as trying a different make. Adtran (TA 750s and TA 850) and Zhone Zplex-10 (A & B). I have another channel bank in the rack immediately above the "wonky" unit one that exhibits no issues. The channel bank in question is connected to a server with a Sangoma Technologies Corp. A104d QUAD T1/E1 AFT card.

Honestly it has been about a month since this issue really started giving me grief everyday again and I forget what happened when I swapped the T1 WAN connection to another server to see if the problem followed the channel bank.

Sometimes I can actually hear relays clicking quite rapidly inside the channel banks in this particular room. Out of all the dozen or so channel banks I am using this one room is the only place where channel banks exhibit this weird behavior. Maybe a ground issue?


Also, I have noticed that sometime on the channels that lose a dial tone if you try to take another call on that channel you get a weird 3 part tone.

Any input on this topic would be greatly appreciated. Let me know if any more information is needed.

Have you stress tested the T-1 in question? I had a situation where a crappy T-1 would allow 12 channels. Any 12, but no more at any given time, to have dial tone.

Sam

Very interesting. Here is the layout:

PRI<---->* PBX<--T1-xover--cable-->CH.BANK<--->24FXS

Do you mean stress test the PRI coming in or the T1 xover cable connected the Asterisk box to the channel bank? The PRI is delivered from L3 on fiber and history has proven those to be really stable for me.

What type of equipment do you suggest I use to do that kind of testing.

btw, thanks for the help!

Is the channel bank pulling PBX dial tone or are you passing circuits direct from the PRI to the distant end? If that's the case, a PRI only has 23 channels and a T-1 has 24 so maybe you've got a congestion issue?

I would start by frogging the circuits to see if the problem follows the PRI or the equipment. I don't know anything about Asterisk boxes, so I can't speak to that part of the puzzle, but you must have a T-1 card in the PC so after you've swapped PRIs and if that's not the problem then swap cards in the PC. the swap the cabling from the PC to the Channel Bank, etc.

Keep working through the circuit till you find the component that's failing - IF IT'S A HARDWARE PROBLEM. If it's a software problem in the Asterix box, then you'll need to talk to the folks in that forum.

To test a T-1 you need a Sunset or a T-Berd or something similar.

Sam

The PBX is providing the dial tone. Yeah, swapping the T1 cards is something I have not tried yet. I'll see if I can do that this morning.

Again, thanks for the help.

The * has real-time activity monitoring. You need to use it to see where the problem is. If you are using dahdi drivers you should have built-in utilities to help you.PM me for further help.

At this point I am pretty sure the T1 card is getting flaky or atleast one port.