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 — Definitions236.72949 C.F.R. § 236.729Cock, double heading.Last amended: 2017Year: 2026Length: 19 wordsOfficial source Cite as 49 C.F.R. § 236.729 (2026)A manually operated valve by means of which the control of brake operation is transferred to the leading locomotive.Previous49 C.F.R. § 236.728Next49 C.F.R. § 236.730