49 C.F.R. § 236.827 System, block signal.
Title 49 - Transportation
A method of governing the movement of trains into or within one or more blocks by block signals or cab signals.
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 G—Definitions
§ 236.827 System, block signal.