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Polycom HDX 7000 ISDN Calls Issue

Ryan Neil
Regular Visitor

Polycom HDX 7000 ISDN Calls Issue



I am currently having an issue with a Polcycom HDX 7000 the symtpoms are as follows,


When initiate a ISDN call it connects and shows the far end on screen for about 10-15 seconds then the camera switches back to me. When it does this the other end shows the word downspeeding on their screen however the call does not disconnect it stays connected but shows the wrong screen the room you are calling from then after another 10-15 seconds it switches back to the far end and stays there permanently with no issues. 


I have checked and compared all the ISDN setttings and call preferences especially the ISDN speed settings and they are the same as all the other sites for the company and none of them have this issue.


Any ideas what could be causing this?







Ryan Neil

Message 1 of 3
Polycom Video EP PLM
Polycom Employee & Moderator

Re: Polycom HDX 7000 ISDN Calls Issue

When the call successfully completes is the call rate used actually a multiple of 64k or 56k?


It could be that somewhere in the path there are 56k trunks and not ISDN trunks and even if you dial at 64k, they could be syncing up at 56k due to the telco.  This happens sometimes between carriers (is the same carrier all the through the path) especially if one of the carriers is a small telco that never upgraded from T1 to PRI.


Or it could be that a switch somewhere in the path is not negotiating 64k properly.

Message 2 of 3

Re: Polycom HDX 7000 ISDN Calls Issue

Hi Polycom Video EP PLM,


Good day.


What kind of test procedure or advise for the condition you mention? We are currently facing issue with downspeeding as well, however that is during the call connecting time.


When we call 512k to another unit in the same site the speed somehow will turn to 448k during the connecting time, and the call not succeed.


both units are HDX 7000 with PRI, settings been confirm with local Service Provider.



Message 3 of 3