800-934-6489 Connect one end of the phone cable to the Tel1 (Voice) port on the rear panel of the modem router. Connect the other end of the phone cable to the telephone. Call Comcast XFINITY customer service at 1-800-XFINITY (1-800-934-6489) or 1-855-OK-BEGIN and ask them to register the phone lines.
Most home alarm systems are supported by Xfinity Voice service, but we recommend that you consult your home alarm company before having Xfinity Voice installed. Because we use our own managed network, and not the public Internet, we can ensure quality of service required to support home alarm systems. Comcast does not guarantee that Xfinity