PURPOSE: To perform adequate initialization once terminal equipment which uses a switching circuit enters into a communication state, by setting a control circuit to an initial address by the polarity inversion detection output signal of an originating circuit or the termination detection output signal of a terminating circuit.

CONSTITUTION: Terminal equipment connected to a network 1 operates under program control. When an opposite subscriber answers after a dial signal is sent out by pressing an origination button 17, the polarity inversion detecting circuit 13 of an originating circuit 12 generates a polarity inversion detection output and inputs it to an OR gate 16; when incoming from the network arrives, the incoming detecting circuit 15 of a terminating circuit 14 generates and inputs an output signal to the OR gate 16. The output of the gate 16 is inputted to a control circuit 4 to set the output of an initial address register 8 in an address register 6 through a control line, and access to a memory 9 stored with programs is attained to read data to an output register 10. Consequently, the terminal equipment is initialized when entering into a communication state without reference to it is in a locked state or runaway state.