(a) is designed for the purpose,

(b) is constructed so that it automatically opens the circuit by gravity and short-circuits the blasting conductor,

(c) has the live side within a fixed locked box accessible only to a person who is conducting the underground blasting operation or a person designated pursuant to paragraph 142(2)(a),

(d) has the door of the box arranged so that it cannot be closed or locked unless the contacts of the device are open and the short circuiting device is in place,

(e) where the power source is from 550 volt circuits, is electromagnetically operated, and

(f) is installed and maintained by a qualified electrician.

(a) is designed for the purpose,

(b) is constructed so that it automatically opens the circuit by gravity and short-circuits the blasting conductor,

(c) has the live side within a fixed locked box accessible only to a person who is conducting the underground blasting operation or a person designated pursuant to paragraph 142(2)(a),

(d) has the door of the box arranged so that it cannot be closed or locked unless the contacts of the device are open and the short circuiting device is in place,

(e) where the power source is from 550 volt circuits, is electromagnetically operated, and

(f) is installed and maintained by a qualified electrician.