(a) When the entire length of a conveyor is visible from the starting
switch, the conveyor operator shall visually check to make certain that all
persons are in the clear before starting the conveyor.
(b) When the entire length of the conveyor is not visible from the
starting switch, a system which provides visible or audible warning shall be
installed and operated to warn persons that the conveyor will be started.
Within 30 seconds after the warning is given, the conveyor shall be started
or a second warning shall be given.