49 C.F.R. § 236.727 Circuit, track; coded.
Title 49 - Transportation
A track circuit in which the energy is varied or interrupted periodically.
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
§ 236.727 Circuit, track; coded.