INTERCOM MASTER UNIT AND INTERCOM SYSTEM

PROBLEM TO BE SOLVED: To transmit video having as high resolution as possible to a radio master unit by enabling communication with the radio master unit through a relay and changing resolution of the video transmitted from a room master unit depending on the number of the relays participating in relaying.SOLUTION: A room master unit 2 comprises: a high frequency communication part 26 for enabling a radio master unit 4 to perform radio response to a call from an entrance slave unit 1; a radio control part 27 for performing transmission/reception of voice data by a time division duplex system while performing transmission of image data by a time division multiple access system; and a master unit CPU 29 having a function for recognizing the number of relays 3 and connection order, and a function for recognizing a relay 3 mediating in a communication route of the radio master unit 4 having performed a call response. The radio control part 27 generates time slots depending on the number of the relays 3 recognized by the master unit CPU 29, and changes allocation of the time slots on the basis of the number of relays actually performing relay operation.