30 C.F.R. § 57.19090 Dual signaling systems.
Title 30 - Mineral Resources
There shall be at least two effective approved methods of signaling between each of the shaft stations and the hoist room, one of which shall be a telephone or speaking tube.
Title 30: Mineral Resources
PART 57—SAFETY AND HEALTH STANDARDS—UNDERGROUND METAL AND NONMETAL MINES
Subpart R—Personnel Hoisting
Signaling
§ 57.19090 Dual signaling systems.
