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WARNING-- wish Cox stop pushing to sell products people don't need and or ask for. I have been customer since November 2014 and never have a need or use battery to operate my modem until a flyer came with monthly bill that I may need one. after received the battery, I installed it immediately. I was thinking having battery will bring improvement "none interrupted/disconnection" of service to the modem. having battery does not reduce the interruption/disconnection that comes every now and then. why push the products that produce no added value to the service customer receives only to maximize company's profit? I hope readers learn from my mistakes not to purchase any product they don't need. Especially residential customer who have been with the company for a long time. that's all I have for now. Thanks to all readers of this article and you are warned. Femi.
Only if your phone is a plain old analog phone that doesn't need AC. Most people have cordless nowadays, so the battery would be essentially a waste.