§  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.

   (b) Rate of interruption. 60 times per minute ±10%.

   (c) Duration of each interruption. 0.5 second ±10%.