These were used for my family's land line in our home. I would prefer to sell all together! One of the handsets was bought in addition to what came in the main package, so it's a tad different, but "speaks" (connects) to the main unit & others.
It was super nice to have the handsets throughout the house (different rooms, including garage and backyard). And best of all, you can use them with their intercom feature to ring internally to different rooms.
Total of 5 handsets. (FYI: I purchased extra, so that I could have more.)
We no longer have a land line & I am downsizing from this house.
I've seen businesses still use similar ones! Maybe you have a purpose for them!