At every shaft or slope in which provision is made in this act for lowering and hoisting persons, a headman and a footman shall be designated by the superintendent or foreman to be at their proper places from the time that persons begin to descend until all the persons who may be at the bottom and at the intermediate landings of said shaft or slope when quitting work shall be hoisted. Such headman and footman shall personally attend to the signals and see that the provisions of this act, in respect to lowering and hoisting persons in shafts or slopes, shall be complied with: Provided, That in slopes where persons are hoisted and lowered and where the tops of such slopes are in clear view or the engineer in charge of the hoisting machinery and where signaling stations or bell buttons are installed along the slope in such manner that the engineer may be promptly signaled to stop the trip in case of need, the footman may accompany the persons ascending or descending the slope and personally perform such duties as are imposed by this act upon the headman and footman. The signaling stations or bell buttons shall be installed at convenient points along the slope, as prescribed by the mine inspector, but in no case shall such signaling stations be separated by more than one hundred feet excepting in such cases where it would be unsafe to use the signaling system because of the pitch of the slope: Provided further, That a headman and footman need not be employed in such cases where a shaft is fitted with an elevator operated by a person employed for that purpose and constructed in such a manner that the top and bottom of the shaft is fitted with doors or gates controlled by the elevators and where the elevator contains all such safety features as are now or may hereafter be commonly used in the operation and installation of elevators.