All joints in conductors shall be mechanically and electrically efficient. Suitable connectors shall be used. All joints of insulated wire shall, after the joint is complete, and in the case of multiconductor, properly staggered, be re-insulated to at least the same extent as the original insulation and¹ shall be effectively sealed so as to exclude moisture. If the cable has metallic armor, ground wires and metallic shielding, mechanical protection and electrical conductivity, equivalent of the original armor shall be provided, and electrical conductivity equivalent to the original conductors likewise provided.