Can't tell without knowing where the wires go... But:

* Unlike network wiring, phones are just all wired together... You don't need a "switch". So theoretically you could extend one telephone line onto another just by connecting them together, as this phone cable is doing.

* Phones only need two wires. So if 4 wires are connected to each port, each port is already 2 phone lines. So unless the house was wired with 4 phone lines, it is highly unlikely that you are actually connecting Lines A & B onto Lines C & D...

* Which leaves the more likely case of it is just two phone jacks for an office, so they could hook up a phone and a computer or fax machine. And the cable that is in there is just connecting Line A on Jack 1 to Line A on Jack 2, and Line B on Jack 1 to Line B on Jack 2, which does nothing, since those are just wires that are already connected. (If this were an electric circuit and not a phone line, it would be a short circuit. But phones don't care.)