Telephony Modem TM502G This cable modem provides not only internet access but with the right service provides Voice Over IP Telephone service on 1 or two lines. Subscription required. Eliminate your monthly rental charge for your telephoney modem. Check with your internet service provider for compatibility. Has been test functional, comes with a small battery that may or may not hold a charge. Batteries are not required for operation, are only used during power outages to maintain phone service which is probably not going to work anyway because your phones will not have power. Not sure why they put batteries in these things. I remove the battery from mine so I can reboot the modem if needed, can not be rebooted with the battery installed.Thanks...Bob Weaver . Please Note