47 CFR §90.317

1. (a)Licensees of systems that have exclusive-use status in their respective geographic areas may engage in fixed ancillary signaling and data transmissions, subject to the following requirements:
   1. (1)All such ancillary operations must be on a secondary, non-interference basis to the primary mobile operation of any other licensee.
   2. (2)The output power at the remote site shall not exceed 30 watts.
   3. (3)Any fixed transmitters will not count toward meeting the mobile loading requirements nor be considered in whole or in part as a justification for authorizing additional frequencies in the licensee's mobile system.
   4. (4)Automatic means must be provided to deactivate the remote transmitter in the event the carrier remains on for a period in excess of three minutes.
   5. (5)Operational fixed stations authorized pursuant to the provisions of this paragraph are exempt from the requirements of §§ 90.425 and 90.429.
   6. (6)If the system is licensed on 470-512 MHz conventional frequencies, and exclusivity has been achieved through the aggregate loading of more than a single co-channel licensee, then a licensee must obtain the concurrence of other co-channel licensees prior to commencing such ancillary operations.
2. (b)Licensees of systems that do not have exclusive-use status in their respective geographic areas may conduct fixed ancillary signaling and data transmissions only in accordance with the provisions of § 90.235 of this part.