Does this phone work without having the 3-AAA batteries in it? Will this telephone work with a headset without installing the 3-AAA batteries? Are the batteries only for backup in case of power outages or something, or are they necessary to operate the telephone?Panasonic KX-TS105B Integrated Business Corded Phone - Black
I have not tried to use the phone without batteries. However, looking at the manual, it does seem to imply that the batteries need to be in place to use a headset. The phone itself will work without batteries, but some of the features won't. You can see the entire manual here: http://service.us.panasonic.com/OPERMANPDF/KXTS105B.PDF
The phone does not come with an AC adapter, so power outtages will not affect it one way or the other.
I have this phone and have never installed the batteries. I think they only are used for remembering numbers. If you don't care about that, you don't need them. Everything else, including speaker functions works great. This is a simple and reliable speakerphone that sounds great.