Sec.  74.531   Permissible service.

   (a) An aural broadcast STL station is authorized to transmit aural program
   material between the studio and transmitter location of a broadcasting
   station, except an international broadcasting station, for simultaneous or
   delayed broadcast.

   (b) An aural broadcast intercity relay station is authorized to transmit
   aural program material between broadcasting stations, except international
   broadcasting stations, for simultaneous or delayed broadcast.

   (c) An aural broadcast intercity relay station is authorized to transmit
   aural program material between noncommercial educational FM radio stations
   and their co-owned noncommercial educational FM translator stations assigned
   to reserved channels (Channels 201 to 220) and between FM radio stations and
   FM translator stations operating within the coverage contour of their
   primary stations. This use shall not interfere with or otherwise preclude
   use of these broadcast auxiliary facilities by broadcast auxiliary stations
   transmitting aural programming between broadcast stations as provided in
   paragraph (b) of this section.

   (d) An aural broadcast STL or intercity relay may be used to transmit
   material between an FM broadcast radio station and an FM booster station
   owned, operated, and controlled by the licensee of the originating FM radio
   station. This use shall not interfere with or otherwise preclude use of
   these broadcast auxiliary facilities by broadcast auxiliary stations
   transmitting aural programming between the studio and transmitter location
   of a broadcast station or between broadcast stations as provided in
   paragraphs (a) and (b) of this section.

   (e) An aural broadcast microwave booster station is authorized to retransmit
   the signals of an aural broadcast STL or intercity relay station.

   (f) Multiplexing of the STL or intercity relay transmitter may be employed
   to provide additional communication channels for the transmission of aural
   program material, news-wire teleprinter signals relaying news to be
   associated with main channel programming, operational communications, and
   material authorized to be transmitted over an FM station under a valid
   Subsidiary Communications Authorization (SCA). An aural broadcast STL or
   intercity relay station may not be operated solely for the transmission of
   operational, teleprinter or subsidiary communications. Operational
   communications include cues, orders, and other communications directly
   related to the operation of the broadcast station as well as special signals
   used for telemetry or the control of apparatus used in conjunction with the
   broadcasting operations.

   (g) All program material, including subsidiary communications, transmitted
   over an aural broadcast STL or intercity relay station shall be intended for
   use by broadcast stations owned or under common control of the licensee or
   licensees of the STL or intercity relay station. Other broadcast stations
   may simultaneously utilize such program material with permission of the STL
   or intercity relay station licensee.

   (h) In any case where multiplexing, is employed on an aural broadcast STL
   station for the simultaneous transmission of more than one aural channel,
   the STL transmitter must be capable of transmitting the multiple channels
   within the channel on which the STL station is authorized to operate and
   with adequate technical quality so that each broadcast station utilizing the
   circuit can meet the technical performance standards stipulated in the rules
   governing that class of broadcasting station. If multiplex operation is
   employed during the regular operation of the STL station, the additional
   circuits shall be in operation at the time that the required periodic
   performance measurements are made of the overall broadcasting system from
   the studio microphone input circuit to the broadcast transmitter output
   circuit.

   [ 28 FR 13716 , Dec. 14, 1963, as amended at  45 FR 51564 , Aug. 4, 1980;  52 FR 31403 , Aug. 20, 1987;  55 FR 50693 , Dec. 10, 1990;  57 FR 41111 , Sept. 9,
   1992]