StacksVerified U.S. regulatory reference

47 CFR §80.74

Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
A “busy” signal, when used by a public coast station in accordance with the provisions of § 80.111(d), must consist of the transmission of a single audio frequency regularly interrupted, as follows:
  1. (a)Audio frequency. Not less than 100 nor more than 1100 Hertz, provided the frequency used for this purpose will not cause auto alarms or selective-ringing devices to be operated.
  2. (b)Rate of interruption. 60 times per minute ±10%.
  3. (c)Duration of each interruption. 0.5 second ±10%.