Distance of radio transmitters to blasting circuit
157An employer and a person who conducts an underground blasting operation shall each ensure that electric detonators are not connected to a source of ignition unless
(a)
every radio transmitter that is closer to a blasting circuit than the distance prescribed in Schedule A has been turned off, and
(b)
every radio transmitter that has not been turned off is prevented from approaching closer to a blasting circuit than the distance prescribed in Schedule A.