PURPOSE: To issue the outgoing and incoming calls of a line wire between a master cordless telephone set and a slave cordless telephone set by a main device provided with central office lines ≥2.

CONSTITUTION: This system is equipped with the main device PQ to which first and second central office lines are connected, plural master cordless telephone sets MQ1-MQn connected in parallel with the main device and bus cables L1-L4, and plural slave cordless telephone sets SQ1-SQm which receive down radio waves emitted from the plural master cordless telephone sets and transmit up radio waves. The main device is equipped with a down radio wave transmission order storage circuit 19, and a maximum electric field strength definition circuit 18 which defines the master cordless telephone set which receives the up radio wave with the maximum electric field strength of plural transmission origin master cordless telephone sets emitting the down radio waves according to the down radio wave transmission order storage circuit. Furthermore, the plural master cordless telephone sets are equipped with speech path forming switches SW1-SW3 which form a speech path between a transmission origin slave cordless telephone set which transmits the up radio wave and an incoming call destination master cordless telephone set with the maximum electric field strength of up radio wave. Furthermore, the plural slave cordless telephone sets are equipped with radio reception circuits 32 which receive the down radio wave, and ringers 36 operated replying to a call by the radio reception circuit.