49 C.F.R. § 236.304 Mechanical locking or same protection effected by circuits.
Title 49 - Transportation
Mechanical locking, or the same protection effected by means of circuits, shall be provided.
Title 49: Transportation
PART 236—RULES, STANDARDS, AND INSTRUCTIONS GOVERNING THE INSTALLATION, INSPECTION, MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES
Subpart C—Interlocking
Standards
§ 236.304 Mechanical locking or same protection effected by circuits.