Rotary telephones are not compatible with Xfinity Voice service.
But in https://forums.xfinity.com/t5/Home-Phone-Features/Pulse-Dialing-Is-It-a-Possibility/m-p/3217253#M509... employee @ComcastJoeTru stated that it might be possible.
This fixes your phone to dial out. It's the easiest little box to hook up, plug and works right away. Plug into the back of your modem where the phone line plugs in and works for the WHOLE house. Took less than 3 seconds to hook up. Costs $40 plus $14 shipping from Australia. its AWESOME!
Thank you for this information. Just noticed your email today. I was aware of the gizmo you suggested. But, although more expensive, did find, what for me, was a better solution. I bought an XLink box which connects by bluetooth to my cell phone. You plug rotary phone into the box and this allows you to not only receive calls, but also to receive calls. Work very well.