PART 23—TELEPHONES AND SIGNALING DEVICES
- 23.1—Purpose.
- 23.2—Definitions.
- 23.3—Application procedures and requirements.
- 23.5—Conditions governing investigations.
- 23.6—General requirements for approval.
- 23.7—Specific requirements for approval.
- 23.8—Inspection and tests.
- 23.9—Special requirements for complete devices.
- 23.10—Material required for MSHA records.
- 23.11—How approvals are granted.
- 23.12—Wording, purpose, and use of approval plate.
- 23.13—Withdrawal of approval.
- 23.14—Instructions for handling future changes in design.