US lawFederal (United States)RegulationsTitle 49 CFR — TransportationChapter II — FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATIONPart 236 — RULES, STANDARDS, AND INSTRUCTIONS GOVERNING THE INSTALLATION, INSPECTION, MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCESSubpart G — Definitions236.72749 C.F.R. § 236.727Circuit, track; coded.Last amended: 2017Year: 2026Length: 12 wordsOfficial source Cite as 49 C.F.R. § 236.727 (2026)A track circuit in which the energy is varied or interrupted periodically.Previous49 C.F.R. § 236.726Next49 C.F.R. § 236.728