[Code of Federal Regulations] [Title 47, Volume 1] [Revised as of October 1, 2002] From the U.S. Government Printing Office via GPO Access [CITE: 47CFR15.21] [Page 683] TITLE 47--TELECOMMUNICATION CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION PART 15--RADIO FREQUENCY DEVICES--Table of Contents Subpart A--General Sec. 15.21 Information to user. The users manual or instruction manual for an intentional or unintentional radiator shall caution the user that changes or modifications not expressly approved by the party responsible for compliance could void the user's authority to operate the equipment.