When there is only one socket in a house or apartment, the incoming line is connected to the two lower receptacles and the upper receptacles are left unused. When a subscriber has more than one telephone socket, they typically are connected so that two telephones can not be connected to the telephone exchange at the same time. This is done by connecting the two upper receptacles of a socket to the lower receptacles of the next socket. When a connected telephone's handset is lifted the two twisted pair connections are separated, thus disconnecting any telephones downward in the chain.