[VoiceOps] Polycom Ghost Ringing

Eric Hiller clec at cygnustel.com
Tue Dec 28 13:19:28 EST 2010

We are having the strangest issue that I have seen for some time. A
customer of ours with Polycom phones (4x ip335, 2x ip550) will
occasionally (maybe 1 in 50 calls) hear ringing on the line along with the
other party. It has happened on both incoming and outgoing calls across
apparently all of the phones. We use ip550 in our office and have never
had such a problem (we run the same firmware as well, although their
hardware is newer). It can be fixed if the person using the phone puts the
other person on hold and then takes them off hold. They have just been
doing this by double pressing hold so the other party doesn't even realize

Call setup on these calls is all normal:

invite from pbx to phone
100 trying from phone to pbx
180 ringing from phone to pbx
200 ok from phone to pbx
ack from pbx to phone
<start rtp>

I have listened to the RTP and there is absolutely no ringing! At this
point I am entirely out of ideas! Does anyone have anything to suggest or
has possibly encountered this before?

Thanks for any ideas or help!

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