For technical questions related to a Cisco Product or Technology, we encourage you to post on the Network Professionals Forum (NetPro). For your specific issue, you can go to IP Telephony forum.
Physical phones we have used are both 7970 and 7975. We could not get the 7937 conference phone to work and we have not tried any of our Gen2 7940 phones. Hope this helps.
Good luck.
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