HT701 not registered and busy tone


I have Xfinity triple service, and just bought myself a modem-router ARRIS SBG7580-AC which I knew later that it does not have phone port. Then I went ahead bought Grandstream HT701 adapter to connect ethernet port and convert it to a phone line. By the way, I have not successfully got the phone to work at all for some reason. The “Phone” light at HT701 never lid, and I’ve been trying to register online, but fail to do so. It’s still show that it’s not registered by the way I got to the way that my phone has a busy tone now (not sure good sign or bad sign). I’ve tried to call my home phone, but it went direct to voicemail. Please help.


I am a little confused -

If you have a triple play with Xfiniti (Comcast), this indicates that you have phone, internet and cable TV. Normally, they would provide the equipment. Xfinity will allow the subscriber to connect their own equipment (to avoid the rental fees) provided that such equipment is approved use on their network. What would normally be used in your case is an eMTA. This is a cable modem with the telephony ports and circuitry built-in. I am assuming the account is a residential account and if such is the case, then I do not know that they will allows a ATA to have access to their closed network. Most cable companies will only support the “approved” equipment and will provision same to work on their network. They are pretty restrictive about what can be connected and even more so about who will setup.

I suggest you call Xfinity and see what they will allow as it not be possible.

Otherwise, I would tell you that you need to have the existing cable modem in bridge mode or pass thru, with the SIP ALG disabled and from there you woould need to port forward 5060UDP and your RTP port (5004?) UDP to the HT701 which should have a static or reserved address. You will need to know the username, authID and password to your phone account as set by Xfinity (not your web portal account password and username). The other issue you face is that if this is a residential account, it is very unlikely that you have a static IP and you will need DDNS…which is another reason that Xfinity may not allow what you are trying to do.

My advice …call Xfinity.


First of, the equipment is not free, I am with them for the second contract now still paying $11 dollars every months until, I started the new contract and decided to get my own equipment. Which the modem router is one of the equipments that compatible with Xfinity and it was on the list. The problem was I did not look closely enough to not see that it would not have the phone port in this one (it was my bad). But I already got it, and I cannot return it then I decided to get the adapter for it and of course I contact Xfinity to help, and they refuse to help me. That’s why I’m here. Hope this is clear. And if any helps would be greatly appreciated. I also have setup ATA to 5060 and RTP to 5004 on the Port forwarding UDP. I have used the User name and password as the Login to Xfinity account, may not be the correct one. I may need to contact Xfinity for that part. Beside ID and Password, do you have anything else that I need to know? Thanks!


I never said anything was free. I indicated that Xfinity will allow subscribers to procure their own in order to avoid paying the rental fees.

However, virtually all cable companies provide the telephony hardware as a function of the telephone subscription without a rental fee. They usually bring in two modems, one for the Internet and the other model, an eMTA or EDVA, for the phones. Some may still use only one modem. Almost all will allow you to bring your own approved MTA (modem), and may allow an approved eMTA/EDVA, but I do not know of a single operator that will allow a subscriber to bring their own ATA (HT) to connect into their network.

It is a closed network. Just like using AT&T or other PSTN provider, you can use any compatible phone you want, but the delivery of the signal to the premise is solely the provider’s bailiwick. Your choices appear to be:

  1. Get Xfinity to provide the equipment needed for the telephone.
  2. Get an eMTA or EDVA
  3. See if you can get out of the contract and find a provider that can use the HT and provide subscriber type telephony services -call fowarding, 3-way, etc.

Finally, the issue you face is that the cable provided telephone service is using Packet Cable which is not pure SIP. If using Packet Cable 1 or 1.5 the eMTA is used and if Packet Cable 2.0, then a EDVA. Packet Cable 2 does use SIP, but again…no HT can take the RF signal and then decode to SIP.


Have they given you details like SIP server, user ID and password for the phone account?

You simply can’t just plug in the ATA in this configuration.


Thank you all for the help. I have contacted Xfinity again, only one option they gave me was to buy a new modem and they did not help me with configurations at all.