The issue discussed in this post is fixed in above software versions with above VOIP ticket.
If you have an issue please open a ticket via your Polycom reseller so we can track this.
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Re: Call Waiting Beep heard for every call coming to main line, only some users
We are on version 5.5.11526 (which is what this doc mentions should have the fix), and it doesn't appear to have that fix. I have confirmed that disabling call waiting (call.callWaiting.enable="0") fixes the problem with BLF activity. Unfortunately disabling call waiting is not an ideal fix though; because that disables the feature. Currently working with our reseller (NetxUSA) to get a case opened with Polycom.