PURPOSE: To simplify connection wiring with subscribers' line or extension by so arranging that an automatic line switching device or message transmitter for connecting the facsimile to the subscriber's line or extension can be provided within the machine room of a private branch exchange.

CONSTITUTION: The automatic line switching device 1 and the facsimile 2 are connected to each other by a pair of communication lines 8. When a call is received from a sole line housed within the private branch exchange 5, the exchange 5 captures an extension 7 to which the device 1 is connected, while the device 1 connects the extension 7 to the facsimile 2 by call signals from the exchange 5. Should a call signal arrive in the interim at the subscriber's line 6, the device 1 connects the line 6 to the message transmitter 4 to issue a message that the line is busy. When a telephone set 3 of the facsimile 2 is hooked off for transmission, the device 1 is actuated to make connection to the subscriber's line or the private line responsive to the originator's dial call through the exchange 5. Should a call be made in the interim to the subscriber's line 6 connected to the device 1, the line 6 is connected to the message transmit ter 4.