When trying to contact Claire's parents, Jake and Claire decide to use the landline so her parents won't recognize the number - and have trouble finding it due to never using it. There are several references that they haven't touched the landline in years, have no use for it, and nobody calls them on it. Yet in an earlier episode they make a big deal about how they're known for putting a lot of time and effort into their regularly changing overproduced outgoing message on the landline, that people call it just to hear their latest message. Cooper ends up asking "What's a landline?", showing it is indeed the landline, not one of their cell phones, and later Cooper is shown playing guitar while Claire's sings a new message, showing how much effort they put into it.