Hi DaveBaugh,

The T25 is a 3.1DOCSIS cable modem you bought that has two1-gigabit speeds. T25  modem provides Ethernet internet and Wi-Fi when connected to a Router  but for the telephonic connection do  connect a telephone cable to the TEL LINE port on the phone and to the Tel1 /Tel 2 port on the rear of the T25.

Check the LEDs of Tel1 and 2 if they flash white, then the Tel1/Tel2 is powered off or a call is in progress.

If the LED lights are Solid White then Tel 1/2 is connected and activated; on-hook.

Activate the Telephone line by contacting your Xfinity/Comcast by providing the MTA MAC ID.

Hope this helps.

Was just going to ask if you had your ISP provision it for the phone. It wouldn’t be the first time they didn’t. Getting in contact with comcast would be ideal

Optimum (nee Cablevision) was unable to provision my T25 for voice. They tried remotely and in person (at my home). No reason; no explanation; they are baffled. I tried contacting Arris before returning the unit, but, got no replies; just this community thing (great customer service ). Worse, I got a mesh network to extend the range of my wireless router, but, now, I cannot get a new modem, because most don’t come with voice anymore (WHY?!?!?), and some have a built-in wireless router, which, according to their own websites, requires a “bridge” in order to work with a mesh network, which may fail and have to be reset during a blackout or a cable company-initiated reboot of the modem.