The lighting system of an aerial mast or tower exceeding 46 meters in height above ground level which is required to have obstruction light shall conform to the following requirements:

(a) there shall be installed at- the top of the mast or tower at least one 100 watt lamp enclosed in aviation red obstruction light globe; and

(b) The light shall burn· from sunset to sunrise and 'shall be so positioned as to ensure unobstructed visibility of the light from aircraft at any normal angle of approach.