I'm changing out an intertel system coming off a lease. On surveying I see 2 female ports on the CO Line bay, on the very lower corner, that are marked Duel LS and duel SL, they have dial tone in and out and no one recognizes the phone number. I wasn't able to sort out the wiring nightmare enough to know where it's going when it leaves the system. Any idea what this port is used for?
