[Code of Federal Regulations] [Title 49, Volume 4] [Revised as of October 1, 2002] From the U.S. Government Printing Office via GPO Access [CITE: 49CFR236.720] [Page 510] TITLE 49--TRANSPORTATION CHAPTER II--FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION PART 236--RULES, STANDARDS, AND INSTRUCTIONS GOVERNING THE INSTALLATION, INSPECTION, MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES--Table of Contents Subpart G--Definitions Sec. 236.720 Circuit, common return. A term applied where one wire is used for the return of more than one electric circuit.