Sec.  22.865   Automatic channel selection procedures.

   

   Link to an amendment published at  70 FR 19310 , Apr. 13, 2005.

   Operation of stations using the channels listed in Sec. 22.857 must be in
   accordance with the procedures in this section.

   (a) A communications channel is not available for use by a ground
   station if it is already in use by another ground station at the same
   location. Ground station equipment must automatically determine
   whether channels are in use by other ground stations at the same
   location, and may employ radio frequency signal monitoring to do so.
   For example, a communications channel may be determined to be in use
   if the received signal power on that channel at the ground station
   exceeds -115 dBm, which, assuming a 0 dB gain 895 MHz receive antenna,
   corresponds to a field strength of approximately 19 dBµV/m. Ground
   stations may employ an alternative method of determining whether a
   communications channel is in use provided that such procedure is at
   least as reliable as radio frequency signal monitoring.

   (b) Data indicating which communications channels are available for
   use are transmitted by ground stations on the assigned control
   channels.

   (c) A call is originated when an airborne mobile station selects a
   communications channel based on the received data from ground stations
   and other factors, and transmits an identification code (which
   identifies the specific ground station from which service is
   requested) on the selected communications channel. The ground station
   from which service has been requested may then obtain any necessary
   billing information and complete the call.

   (d) A ground station may not transmit on a communications channel
   unless it has received the proper identification code. After a ground
   station has begun to transmit on a communications channel, that
   channel is not available to ground stations other than the one from
   which service has been requested until the call is terminated.

   (e) A call is terminated by the ground station when either a hang-up
   signal is transmitted by the airborne mobile station, or the signal
   from the airborne mobile station on the communications channel is lost
   for a period of 15 continuous seconds. The hang-up signal is the
   on-off keying (50% duty cycle) of an unmodulated carrier over a period
   of one second with pulse duration of 5 milliseconds. However, if all
   carriers authorized to operate air-ground systems using the channels
   listed in Sec. 22.857 agree that an alternative hang-up signal and/or
   procedure would be more efficient or beneficial, such alternative
   hang-up signal and/or procedure may be used. The carriers must jointly
   give prior notification to the FCC if an alternative hang-up signal
   and/or procedure is used.