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Echo problem with IPS2000

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phadobas

Technical User
Jul 30, 2005
612
US
I have an IPS2000 with some IP phones and with some TDM phones. The IP phones are off-site, connecting to the pbx via a point-to-point T1 that connects to Cisco routers which "convert" IP traffic to the T1 protocol and back to IP on the other end. Outgoing calls are sent out on a PRI.
This IPS2000 has a CCIS connection to a 2400ICS and can do sta-to-sta dialing between the 2 systems just fine.
The problem is as follows: intermittent reports from the IPS users about echo on the line. Apparently, this is mostly noticed on calls across the CCIS over to the 2400ICS. I don't live near the site, and rarely ever can I make it there. I can't reproduce the problem. But due to the number of reports, it appears to be a valid problem. Recently, not only did it get confirmed by more users, but now I got report from the TDM phone users too - all the while I thought it was only a problem with the IP phones, and was due to delayed packets across the IP network and the T1. But now, as I said, somebody complained from a TDM phone too, which doesn't invlove ANY IP hops.
If I have an IP problem, I have to say, it will stay as I'm not in a position to redo the remote-site connection with some higher-capacity line.
However, I'm thinking that I may have to fiddle with the PAD settings on the CCIS line, as all reports seem to come about calls accross the CCIS. No one ever complained about outgoing calls on the PRI.
I'm very familiar with both the IPS2000 and the 2400ICS, yet never in my life did I have to deal with PAD settings. Things like "If I change the PAD settings, do I have to pull / re-insert the CCSI card, or does the change take effect immediately?". And another stupid question that somehow I could not figure out from the manuals: "Does a higher PAD setting (or higher DB) increase the volume on the line or decrease?"
On another note, most users use wireless headsets on the IPS (very high-end headsets), and I already told them to lower the mic sensitivity, which they did, and that DID handle a certain aspect of what they were hearing. But the "delayed hear yourself" syndrome still exists.
I've been hearing reports for many years from the users, and I could never fully handle it. I went through the command manual of both systems, searhing for echo-related commands, but everything I found, was already activated to reduce/handle echo. I upgraded the IP-PAD card on the IPS as well.
Any ideas, pointers, suggestions?
 
db is a sliding algorithmic scale. A small change creates a big difference. Typically a TDM to TDM connection rarely experiences echo. However, there may be repeaters involved, or even the central office converting to TDM to IP and back again. Most CO's are making that switch.
In any case, padding the route to lower volume usually helps the situation.
There are two types of padding available to the IPS, fixed and flexible. The flexible padding offers more options.
First, check the current pad setting in CMD 3519> CCIS RT>? 7 is the default value.
7, for a station to DTI/PRI/CCIS connection = -3 transmit and -8 receive padding. A higher minus number equals more volume drop.
You could try -8 tx and -8 rec, by setting CMD 3519 to 0, CMD 42>50>02. Refer to the beginning of CMD 3519 in the command manual for the various tables and connection patterns.
EX: (CCIS RT = 30)
3519>30>50
42>50>02
There is some debate as to weather the change takes affect immediately, after all trunks go idle or you need to reset the CCIS card.
 
That was very educational. Thank you for all the info there. It clears up a lot of questions. I'll start experimenting.
 
The setting for CMD3519>CCIS> was 5, which meant -3 receive and -3 transmit for PAD setting. I changed that to CMD>3519>CCIS>7, which made it -8 receive and -3 transmit. So only the receive volume changed - lowered it. I made a test call before the change and about 30 seconds after the change. There was a noticable drop in volume on my end (receive) while the other party didn't notice any change in volume (transmit volume didn't change).
The problem is that the echo is intermittent, and of course I was unable to duplicate it BEFORE I made the change and after the change was done. So I'll observe the situation and hope for the best. Volume settings were never fiddled with on this system before in the quest of handling the echo, so it might very well solve it.
Fingers crossed.
 
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