On a recent install, we used several CP-7575G phones with the UC560. There is a mix of 7975Gs and 508Gs. On the 7975s, when there is silence on a call, the 7975 user can hear noise - to us it sounds like a modem negotiating faintly in the background and loops endlessly. You hear light (ordinary) static/hissing on the 508s but cannot hear this same sound. This customer is using a SIP trunk and there is not any analog involved.
We tested against several different phone types (cell/land) on the other end to ensure it wasn't coming from the other side. The other party could not hear anything.
Could it be because the 7975G is a "wideband" device and it's picking up other noise you wouldn't normally hear?
It would figure, the users heard it within the first 5 minutes of getting their new phones. Any suggestions?
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