Sec. 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 Sec. 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.
    (b) Rate of interruption: 60 times per minute &177; 10%.
    (c) Duration of each interruption: 0.5 second &177; 10%.