PURPOSE: To lower the ground surge impedance and an earth resistance by connecting a messenger wire grounding of a communication cable and the ground buried beneath the mount location of a subscriber protector by means of a ground conductor and using it as the ground for the protector.

CONSTITUTION: The ground electrode 8 is buried beneath the housing mount location of the subscriber protector 3 via a ground conductor 7 and the ground conductor 9 is prolonged up to the cable messenger wire 5 from the housing mount location of the protector 3 and connected thereto. Thus, the messenger grounding 6 and the electrode 8 are connected together and the connected grounding is used as the grounding for the protector 3. Through the constitution above, the residual voltage in applying a lightening surge to the protector 3, is dropped tentatively to zero potential by the grounding effect comprising the conductor 7 and the electrode 8 and decreased by the grounding 6 even after 2∼3μsec after the operation of arrester.