Sec. 27.4  Terms and definitions.

    Assigned frequency. The center of the frequency band assigned to a 
station.
    Authorized bandwidth. The maximum width of the band of frequencies 
permitted to be used by a station. This is normally considered to be the 
necessary or occupied bandwidth, whichever is greater.
    Average terrain. The average elevation of terrain between 3 and 16 
kilometers from the antenna site.
    Base station. A land station in the land mobile service.
    Effective Radiated Power (ERP) (in a given direction). The product 
of the power supplied to the antenna and its gain relative to a half-
wave dipole in a given direction.
    Equivalent Isotropically Radiated Power (EIRP). The product of the 
power supplied to the antenna and the antenna gain in a given direction 
relative to an isotropic antenna.

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    Fixed service. A radio communication service between specified fixed 
points.
    Fixed station. A station in the fixed service.
    Land mobile service. A mobile service between base stations and land 
mobile stations, or between land mobile stations.
    Land mobile station. A mobile station in the land mobile service 
capable of surface movement within the geographic limits of a country or 
continent.
    Land station. A station in the mobile service not intended to be 
used while in motion.
    Mobile service. A radio communication service between mobile and 
land stations, or between mobile stations.
    Mobile station. A station in the mobile service intended to be used 
while in motion or during halts at unspecified points.
    National Geodetic Reference System (NGRS). The name given to all 
geodetic control data contained in the National Geodetic Survey (NGS) 
data base. (Source: National Geodetic Survey, U.S. Department of 
Commerce)
    Portable device. Transmitters designed to be used within 20 
centimeters of the body of the user.
    Radiodetermination. The determination of the position, velocity and/
or other characteristics of an object, or the obtaining of information 
relating to these parameters, by means of the propagation properties of 
radio waves.
    Radiolocation. Radiodetermination used for purposes other than those 
of radionavigation.
    Radiolocation land station. A station in the radiolocation service 
not intended to be used while in motion.
    Radiolocation mobile station. A station intended to be used while in 
motion or during halts at unspecified points.
    Radionavigation. Radiodetermination used for the purpose of 
navigation, including obstruction warning.
    Satellite Digital Audio Radio Service (satellite DARS). A 
radiocommunication service in which compact disc quality programming is 
digitally transmitted by one or more space stations.
    Time division multiple access (TDMA). A multiple access technique 
whereby users share a transmission medium by being assigned and using 
(one-at-a-time) for a limited number of time division mulitplexed 
channels; implies that several transmitters use one channel for sending 
several bit streams.
    Time division multiplexing (TDM). A multiplexing technique whereby 
two or more channels are derived from a transmission medium by dividing 
access to the medium into sequential intervals. Each channel has access 
to the entire bandwidth of the medium during its interval. This implies 
that one transmitter uses one channel to send several bit streams of 
information.
    Wireless communications service. A radiocommunication service that 
encompasses fixed, mobile, satellite DARS, and radiolocation services.
[ 62 FR 9658 , Mar. 3, 1997, as amended at  62 FR 16497 , Apr. 7, 1997]