Lobby caster machine, door phone system and communication method

摘要

To provide a lobby entrance handset capable of performing digital communication with an indoor monitor master unit by using an existing 2-wire cable wired in a star pattern.SOLUTION: A first control part 107 is configured so as to, when a piece of room number information and a call signal are input from a second control part 116 in a stand-by state, select an indoor monitor master unit 200 corresponding to the room number information as the communications partner, and to output a routing signal representing the selection as the communications partner to a cable selection-connection part 101 and to generate a connection request. The cable selection-connection part 101 is configured to connect a terminal T12-I connected to the indoor monitor master unit 200 as the communications partner, a receiving driver 111 and a sending driver 110 according to the routing signal.SELECTED DRAWING: Figure 3