[Code of Federal Regulations] [Title 49, Volume 4] [Revised as of October 1, 2007] From the U.S. Government Printing Office via GPO Access [CITE: 49CFR236.104] [Page 645] TITLE 49--TRANSPORTATION CHAPTER II--FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION PART 236_RULES, STANDARDS, AND INSTRUCTIONS GOVERNING THE INSTALLATION, Subpart A_Rules and Instructions: All Systems Sec. 236.104 Shunt fouling circuit. Shunt fouling circuit shall be inspected and tested at least once every three months.