It shall be unlawful for any railroad carrier, its officers or agents, to require or permit any employee to be or remain on duty for a longer period than sixteen consecutive hours. For the purposes of this section, employees shall mean any person actually engaged in or connected with the movements of any train. Whenever any such employee of such common carrier shall have been continuously on duty for sixteen hours, he shall be relieved and not be permitted or required to again go on duty without having at least ten consecutive hours’ rest off duty, and no such employee, who has been on duty sixteen hours in the aggregate in any twenty-four-hour period, shall be required or permitted to continue or again go on duty without having had at least eight consecutive hours off duty; Provided, no operator, train dispatcher, or other employee who by the use of the telegraph, or telephone, dispatches reports, or transmits, receives, or delivers orders pertaining to or affecting train movements shall be required or permitted to be or remain on duty for a longer period than nine hours in any twenty-four-hour period in all towers, offices, places, and stations continuously operated day and night nor for a longer period than thirteen hours in all towers, offices, places, and stations operated only during the daytime, except in cases of emergency, when the employees named in this proviso may be permitted to be or remain on duty for four additional hours in a twenty-four-hour period and not to exceed three days in any one week. The commission may, after full hearing in a particular case, and for good cause shown, extend the period within which a common carrier shall comply with the provisions of this section.