Problems with VS4000 only connects a 384

[raeman]

Hi All,

Here is my problem. I have a VS400 and 4 ISDN lines. First Everything has worked before with no problems.. Second I have talked to the Telco and they have tested all my ISDN lines and they are fine. When I try to connect a 512 it connects but the video is choppy and sound distorted intermittently. This usually happens a couple of times a minute for only a second or so, sometimes the lighting bolt comes on the screen as well. When I drop the speed to 384 everything works fine and is stable for hours on end. As I stated before everything has worked fine before. There have been no updates to the system either. Does anybody have any ideas??

Thanks in advance..

RaeMan

[Harvell]

It could be two things... your imux or the ISDN lines. Try swapping lines 3 and 4. Also change the SPID numbers respectfully. If you get the same errors on a 384k call with line 4 on port 3 then you know that the line has issue's. Or you could try line 4 in port 1 of the IMUX and try a 128k call. If all is well and known good ISDN lines are not working on port 4 then try reloading software or try reclaiming the flash on the 4k.

If you get errors from line 4 then have the telco run a D-channel trace to find out the problem. Sometimes they just run a BERT test to check the copper in the wires.

[raeman]

Thanks for the info.. the telco did both tests. so i will try the other test of switching the lines and see what result I get.

thanks

[raeman]

Ok I have switched line 4 B1 and B2 to the 3rd line. Move the cables and changed the numbers in the systems as necessary and then tried a 384 call. And... Drum roll... it works just fine. So this tells me I have a problem with either the IMUX or the NT1 device? My guess is that I will have to replace one of these devices and see if the problem goes away, to determine which is the problem. Anybody got a better Idea.. Because I don't have a spare IMUX or a spare NT1??

I did have the telco out and they did all kinds of tests on all the lines and they are fine.

Thanks

[Cornish]

You might want to try each ISDN line seperately and try 128k calls with each. Just because you're connecting at 384k doesn't mean your codec's using the first 3 lines.

Here's what I'd try:

Disconnect L2, L3, L4 and make the call.
Disconnect L1, L3, L4 and make the call.
Disconnect L1, L2, L4 and make the call.
Disconnect L1, L2, L3 and make the call.
Note that I'm not suggesting you swap ports yet.

When (if) the problem happens with a single line, you'll need to try it in another port of your IMUX to determine whether it's the line or the IMUX that's the problem.

Let us know how it goes!