PURPOSE: To stop the function of a communication adaptor which becomes unnecessary without adding any new instruction, etc., especially by installing a function stopping means which stops the function of the adaptor when frames, in which its own address is used as the sending source address and sending destination address, are continuously received plural times to the communication adaptor.

CONSTITUTION: A function stopping means 4 which stops the function of a communication adaptor 2 when frames, in which its own address is used as the sending source address and sending destination address, are continuously received plural times is installed to the communication adaptor 2. Therefore, when standby terminal equipment 3 continuously sends such signals plural times, the function of the communication adaptor 2 of the currently used terminal equipment, in which a fault occurs, is stopped. Thus the function of the communication adaptor 2 which becomes unnecessary can be stopped without adding any new instruction, etc., especially.