Section 90.557 - Secondary fixed signaling operationsTrunked and conventional 700 MHz narrowband systems may conduct fixed ancillary signaling and data transmissions subject to the following requirements:
(a) Operations are permitted only on:(1) Narrowband State License channels specified in § 90.531(b)(5) , subject to the discretion of the relevant State licensee; and(2) Narrowband General Use channels specified in § 90.531(b)(6) , subject to the discretion of the regional planning committee.(b) All operations must be on a secondary, non-interference basis to the primary mobile operation of any other licensee.(c) The output power at the remote site must not exceed 30 watts.(d) 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.(e) Operational fixed stations authorized pursuant to this section are exempt from the requirements of §§ 90.425 , 90.429 , and 90.559 .(f) Any operations undertaken in a shared use environment must be conducted pursuant to an agreement between the licensee and each participant, as set forth in § 90.179 .79 FR 39341, July 10, 2014