47 C.F.R. § 74.550
Each authorization for aural broadcast STL, ICR, and booster stations shall require the use of equipment which has received a grant of certification or authorized under a Supplier's Declaration of Conformity. Equipment which has not been approved under the equipment authorization program and which was in service prior to July 1, 1993, may be retained solely for temporary uses necessary to restore or maintain regular service provided by approved equipment, because the main or primary unit has failed or requires servicing. Such temporary uses may not interfere with or impede the establishment of other aural broadcast auxiliary links and may not occur during more than 720 cumulative hours per year. Should interference occur, the licensee must take all steps necessary to eliminate it, up to and including cessation of operation of the auxiliary transmitter. All unapproved equipment retained for temporary use must have been in the possession of the licensee prior to July 1, 1993, and may not be obtained from other sources. Equipment designed exclusively for fixed operation shall be authorized under Supplier's Declaration of Conformity procedure. The equipment authorization procedures are contained in subpart J of part 2 of this chapter.
47 C.F.R. §74.550
The Declaration of Conformity procedure has been replaced by Supplier's Declaration of Conformity. Equipment previously authorized under subpart J of part 2 of this chapter may remain in use. See §2.950 to this chapter.
Consistent with the note to §74.502(a), grandfathered equipment in the 942-944 MHz band and STL/ICR users of these frequencies in Puerto Rico are also required to come into compliance by July 1, 1993. The backup provisions described above apply to these stations also.