[Code of Federal Regulations] [Title 30, Volume 1] [Revised as of July 1, 2006] From the U.S. Government Printing Office via GPO Access [CITE: 30CFR77] [Page 649] TITLE 30--MINERAL RESOURCES CHAPTER I--MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR PART 77_MANDATORY SAFETY STANDARDS, SURFACE COAL MINES AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES--Table of Contents Subpart J_Low- and Medium-Voltage Alternating Current Circuits Sec. 77.902-1 Fail safe ground check circuits; maximum voltage. The maximum voltage used for ground check circuits under Sec. 77.902 shall not exceed 40 volts.