PURPOSE: To send efficiently a 50bps data of a low speed telex terminal equipment by connecting a telex terminal equipment TA between a telex terminal equipment and a network terminator so as to apply packet forming of D- channel.

CONSTITUTION: When a call signal is sent from a telex terminal equipment 1 to its terminal adaptor 2, an adaptor TA2 sends a Layer 2 setting signal SABM of a D channel packet to the network terminator 3. Then the process enters the packet forming stage and when a selection signal is sent from the terminal equipment 1 to the adaptor 2, an I(X, P) being an information frame of a digital incorporation service network ISDN is sent to the equipment 3 from the adaptor 2 as CR information of packet forming. A character data Data is stored in a storage section 22 from the terminal equipment 1 via an existing interface section 20 in the data transfer phase and sent to the equipment 3 via an ISDN subscriber interface section 231 and a driver 232.