xfinifty voice analog or digital

Their home phone service is VOIP between the Voice modem or gateway device in your home and Comcast, but the phone jacks on that device provide a POTS (analog "Plain Old Telephone Service") interface to the touch-tone wireline telephone(s) in your home. They don't allow customer IP phones to access their home phone system directly.

Yes I was told the Ethernet on that modem is for voice, is that correct? also xifinity voice is VoIP then why use RJ11 or analog phone line connect? VoIP should use Ethernet and VoIP handset also use Ethernet connection.

The modem is installed in basement next to outside wire, then phone line come out upstairs, and connected to old analog phone.  but why the setup is like that, since voice is voIP should use voip phone system ?  

is it possible that I use analog to digital ATA adapter connect phone line connect to Ethernet on IP phone handset ?

Your cable modem is a data modem and an eMTA (see https://en.wikipedia.org/wiki/Cable_modem#MTA). The Ethernet jack is NOT for home phone voice, it provides an Internet connection (if that's how the device is configured) and the RJ11 jacks provide their Voice home phone service. The modem/eMTA converts between POTS handset signals and the digital ones sent to and from Comcast. To use an Ethernet connected VOIP handset you'd need to subscribe to a service that provides such arrangements. Comcast does not.

Yes the modem is installed that way.  so even I use use analog to digital ATA adapter connect phone line connect to Ethernet and use voip IP phone handset it will not work?  or is not allowed by Comcast ?   The voice can only  or must use RJ11 phone line port?  what about DECT 6.0 phones ?

can i use DECT 6.0 phone like Motorola AXH01 DECT 6.0 Smart Cordless Phone  ?

can i use DECT 6.0 phone like Motorola AXH01 DECT 6.0 Smart Cordless Phone  ?

With the base unit connected to the RJ-11 and Ethernet jacks, I think so.

even I use use analog to digital ATA adapter connect rj11 phone line to Ethernet on voip IP phone handset it will not work? is that right?  

even I use use analog to digital ATA adapter connect rj11 phone line to Ethernet on voip IP phone handset it will not work? is that right?

A VOIP handset would only work with their Voice home phone service if that handset also had a POTS interface and was connected to one of the RJ-11 jacks, or to a base unit connected to one of them. As stated above, they don't allow customer IP phones to access their home phone system directly.

You can use an IP phone over a Comcast Internet connection, but only if you have VOIP service from another provider. It's not something they offer.

you indicated Comcast must use RJ11 connection, don't allow customer IP phones to access their home phone system directly.  but when I convert RJ11 to RJ45 is not direct connect IP phone.  IP phone handset have better audio and lots of feature, regular cordless phone have none, and RJ11 by default does not support voip.  

Not all voip service need RJ11.  The captel  phone use Ethernet connect for caption and use RJ11 for phone.  

most voip use Ethernet directly connect voip handset.  

... IP phone handset have better audio and lots of feature ...

But requires a VOIP provider. Please reread my earlier messages.

yes I know IP phone require a voip provider. 

now you indicate Comcast voice must use RJ11 connection.   can you recommend some phones can use? 

... can you recommend some phones can use?