---
kind: "section"
citation: "47 C.F.R. § 90.637"
title: "47"
number: "90.637"
heading: "Restrictions on operational fixed stations."
url: "https://uscodex.org/cfr/47/90.637"
---

# §90.637. Restrictions on operational fixed stations.

- (a) Except for control stations, operational fixed operations will not be authorized in the 806-824 MHz, 851-869 MHz, 896-901 MHz, or 935-940 MHz bands. This does not preclude secondary fixed tone signaling and alarm operations authorized in [§ 90.235](/cfr/47/90.235.md) or in [paragraph (c)](#c) of this section.
- (b) Control stations associated with one or more mobile relay stations will be authorized only on the assigned frequency of the associated mobile station. Use of a mobile service frequency by a control station of a mobile relay system is subject to the condition that harmful interference shall not be caused to stations of licensees authorized to use the frequency for mobile service communications.
- (c) Trunked and conventional systems that have exclusive-use status in their respective geographic areas may conduct fixed ancillary signaling and data transmissions subject to the following requirements:
  - (1) All operations must be on a secondary, non-interference basis to the primary mobile operation of any other licensee.
  - (2) The output power at the remote site must not exceed 30 watts.
  - (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) 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) Operational fixed stations authorized pursuant to the provisions of paragraphs [(c)](#c) and (d) of this section are exempt from the requirements of §§ [90.425](/cfr/47/90.425.md) and [90.429](/cfr/47/90.429.md).
- (d) Conventional 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 all the provisions of [§ 90.235](/cfr/47/90.235.md).

## Notes

### Amendments

[47 FR 41032, Sept. 16, 1982, as amended at 48 FR 51929, Nov. 15, 1983; 49 FR 36377, Sept. 17, 1984; 51 FR 37405, Oct. 22, 1986; 52 FR 1332, Jan. 13, 1987; 53 FR 12157, Apr. 13, 1988; 57 FR 34693, Aug. 6, 1992]

### Authority

Authority: 47 U.S.C. 154(i), 161, 303(g), 303(r), 332(c)(7), 1401-1473

### Source

Source: 43 FR 54791, Nov. 22, 1978, unless otherwise noted.

### Amendments

[47 FR 41032, Sept. 16, 1982, as amended at 48 FR 51929, Nov. 15, 1983; 49 FR 36377, Sept. 17, 1984; 51 FR 37405, Oct. 22, 1986; 52 FR 1332, Jan. 13, 1987; 53 FR 12157, Apr. 13, 1988; 57 FR 34693, Aug. 6, 1992]