Under Singapore Workplace Safety and health (General provisions) Regulations,
(7) In every workplace, there shall be effective warning devices that
(a) are capable of being operated without exposing any person to undue risk;
(b) are maintained and tested at least once every month;
(c) give warning in case of fire; and
(d) are clearly audible throughout the workplace.
In construction sites where there is no electricity, the manual rotate bell will fulfill this requirement.
In a fire or when there is a sudden blackout with no electricity, the Hercules manual rotate bell will still work. Usually installed at fire points with high visibility.
As it is mechanically operated, no maintenance is required. To operate, simply rotate handle in a single direction.