PURPOSE: To attain an automatic incoming state even at a terminal where a power supply is not applied yet by shifting the communication right to another terminal from a specific one when a communicatable state is secured with application of the power supply of another terminal corresponding to a subaddress after the specific terminal detects an incoming state and decides the subaddress.

CONSTITUTION: A communication right control system contains a master terminal 13 which is connected to a DSU 11 via a bus 12 and plural slave terminals 14. The terminal 13 shifts to a communication state in response to the call setting signal received from a network. Then the terminal 13 analyzes a subaddress, controls the application of the power supply of terminals 14, and transmits an interruption signals to the network in a workable state. Each of terminals 14 analyzes an E bit received from the DSU 11. If this analyzing result shows an interruption signal sent from the terminal 13, a call restart signal is transmitted with use of a call number equal to that designated in the interruption signal. Thus a terminal 14 shifts to a communication state in place of the terminal 13.