Oki 5700 - Manual (Page 35)

English
Installation 3-7
Connecting Telephone Line
1 Plug one end of the telephone line cable into the LINE socket
(uppermost telephone socket) on the rear of the machine.
2 Plug the other end of the cable into the wall telephone socket.
Note:
Be sure to connect this line before connecting external telephone or
optional handset to the machine.
Connecting External Telephone/Answering Machine
1 Plug the telephone cable into the TEL socket (located immediately
below the LINE socket) on the rear of the machine. (In certain countries
it may be necessary to use a telephone plug adapter).