PURPOSE: To improve the rotating efficiency for point-to-point exclusive connection, by providing a discriminating function for same slave station control means, in a data communication system.

CONSTITUTION: The user designates point-to-point or multi-point informing system for a slave station. Through this designation, a slave station control program gives information to a communication control program with a channel command word CCW. The communication control program discriminates the connection whether it is point-to-point or multi-point with the CCW information, and when it is the point-to-point connection, a carrier channels are remained ON and when it is the multi-point connection, the carrier control is done. Thus, in case of the point-to-point connection, the time for the carrier channel control can be saved.