[Code of Federal Regulations] [Title 14, Volume 3] [Revised as of January 1, 2006] From the U.S. Government Printing Office via GPO Access [CITE: 14CFR171.21] [Page 219] TITLE 14--AERONAUTICS AND SPACE CHAPTER I--FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PART 171_NON-FEDERAL NAVIGATION FACILITIES--Table of Contents Subpart B_Nondirectional Radio Beacon Facilities Sec. 171.21 Scope. (a) This subpart sets forth minimum requirements for the approval and operation of non-Federal, nondirectional radio beacon facilities that are to be involved in the approval of instrument flight rules and air traffic control procedures related to those facilities. (b) A nondirectional radio beacon (``H'' facilities domestically-- NDB facilities internationally) radiates a continuous carrier of approximately equal intensity at all azimuths. The carrier is modulated at 1020 cycles per second for station identification purposes. [Doc. No. 5034, 29 FR 11337, Aug. 6, 1964, as amended by Amdt. 171-2, 31 FR 5408, Apr. 6, 1966; Amdt. 171-7, 35 FR 12711, Aug. 11, 1970]