PURPOSE: To prevent oscillation and fluctuation of output signal from a tape recorder by providing a limiting resistance for preventing abnormal oscillation in the input section.

CONSTITUTION: A limiting resistance 18 is provided between an earth side terminal 14 that constitutes input section of an interface section and a ground. Reproduction output from a tape recorder 1 is supplied from terminals 6, 7 to the interface side. When the output fluctuates, the level of the earth terminal 7 of output section is also changed by change of output current. By providing the limiting resistance 18, the ground level between apparatus 1, 8 is balanced and the current component that flows in (l) line decreasees. Accordingly, the ground potential Vout of output section of tape recorder side 1 can be made nearly equal to the ground potential Vin of the interface section.