Telephone service or equivalent two-way communication facilities shall be provided in all mines at least one of which shall be in service at all times as follows:

(a) A telephone or equivalent two-way communication facility shall be located on the surface within five hundred feet of all main portals, and shall be installed either in a building or in a box-like structure designed to protect the facilities from damage by inclement weather. At least one of these communication facilities shall be at a location where a responsible person who is always on duty when miners are underground can hear the facility and respond immediately in the event of an emergency. "Two-way communication facility" shall mean a system maintained to allow voice contact to come in and out of the working section at all times.

(b) (1) Telephones or equivalent two-way communication facilities provided at each working section shall be located not more than five hundred feet outby the last open crosscut and not more than eight hundred feet from the farthest point of penetration of the working places on such section.

(2) The incoming communication signal shall activate an audible alarm, distinguishable from the surrounding noise level, or a visual alarm that can be seen by a miner regularly employed on the working section.

(3) If a communication system other than telephones is used and its operation depends entirely upon power from the mine electric system, means shall be provided to permit continued communication in the event the mine electric power fails or is cut off: Provided, That where trolley phones and telephones are both used, an alternate source of power for the trolley phone system is not required.

(4) Telephones or equivalent two-way communication facilities shall be maintained in good operating condition at all times. In the event of any failure in the system that results in loss of communication, repairs shall be started immediately, and the system restored to operating condition as soon as possible.

(5) Where required by the director, trucks used for haulage of coal, miners, or supplies by an operator shall be equipped with two-way communication instruments.

(c) On or after January 1, 1978, unless the director for good cause grants a waiver, all such telephones or equivalent two-way communications shall be connected to regular telephonic and other means of communication available in the community so that in the event of an emergency, emergency medical attendants or other personnel can communicate to and from the mine directly to health care facilities.

(d) Telephone lines and cables shall be carried on insulators installed on the opposite side from power or trolley wires, and where they cross power or trolley wires, they shall be insulated adequately. Lightning arrestors shall be provided at the points where telephone circuits enter the mine.