47 CFR 80.74 - Public coast station facilities for a telephony busy signal.
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:
(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.
Title 47 published on 2013-10-01
no entries appear in the Federal Register after this date.