A housephone is a telephone that only makes calls inside the same building, especially a hotel. From your room you can ring the front desk, room service, or another room — not your family in another city, unless the hotel has also given you an outside line. Office buildings sometimes have the same kind of inside-only phone. People also write it as house phone (two words) or say internal phone. House here means “this building,” not “the family home.”

內線電話、館內電話（飯店客房打給櫃檯或別間房的那種，不是家裡的市話）