30 C.F.R. § 23.6 General requirements for approval.
Title 30 - Mineral Resources
Telephones and signaling devices shall be durable in construction, practical in operation, and suitable for conditions of underground service. They shall offer no probable explosion hazard under normal operation if use in gassy or dusty mine atmospheres.
Title 30: Mineral Resources
PART 23—TELEPHONES AND SIGNALING DEVICES
§ 23.6 General requirements for approval.
