Sec.  2.201   Emission, modulation, and transmission characteristics.

   The following system of designating emission, modulation, and transmission
   characteristics shall be employed.

   (a) Emissions are designated according to their classification and their
   necessary bandwidth.

   (b)  A  minimum  of  three  symbols  are  used  to  describe the basic
   characteristics of radio waves. Emissions are classified and symbolized
   according to the following characteristics:

   (1) First symbol—type of modulation of the main character;

   (2) Second symbol—nature of signal(s) modulating the main carrier;

   (3) Third symbol—type of information to be transmitted.

   Note: A fourth and fifth symbol are provided for additional information and
   are shown in Appendix 6, part A of the ITU Radio Regulations. Use of the
   fourth and fifth symbol is optional. Therefore, the symbols may be used as
   described in Appendix 6, but are not required by the Commission.

   (c) First Symbol—types of modulation of the main carrier:
     (1) Emission of an unmodulated carrier N
     (2) Emission in which the main carrier is amplitude-modulated (including
   cases where sub-carriers are angle-modulated):
   —Double-sideband A
   —Single-sideband, full carrier H
   —Single-sideband, reduced or variable level carrier R
   —Single-sideband, suppressed carrier J
   —Independent sidebands B
   —Vestigial sideband C
     (3) Emission in which the main carrier is angle-modulated:
   —Frequency modulation F
   —Phase modulation G

   Note: Whenever frequency modulation “F” is indicated, Phase modulation “G”
   is also acceptable.
     (4) Emission in which the main carrier is amplitude and angle-modulated
   either simultaneously or in a pre-established sequence D
     (5) Emission of pulses:^1
   —Sequence of unmodulated pulses P
   —A sequence of pulses:
   —Modulated in amplitude K
   —Modulated in width/duration L
   —Modulated in position/phase M
   —In which the carrier is angle-modulated during the period of the pulse Q
   —Which is a combination of the foregoing or is produced by other means V
     (6) Cases not covered above, in which an emission consists of the main
   carrier modulated, either simultaneously or in a pre-established sequence,
   in a combination of two or more of the following modes: amplitude, angle,
   pulse W
     (7) Cases not otherwise covered X


   ^1 Emissions where the main carrier is directly modulated by a signal which
   has been coded into quantized form (e.g. pulse code modulation) should be
   designated under (2) or (3).

   (d) Second Symbol—nature of signal(s) modulating the main carrier:
     (1) No modulating signal 0
     (2) A single channel containing quantized or digital information without
   the use of a modulating sub-carrier, excluding time-division muliplex 1
     (3) A single channel containing quantized or digital information with the
   use of a modulating sub-carrier, excluding time-division multiplex 2
     (4) A single channel containing analogue information 3
     (5) Two or more channels containing quantized or digital information 7
     (6) Two or more channels containing analogue information 8
     (7) Composite system with one or more channels containing quantized or
   digital information, together with one or more channels containing analogue
   information 9
     (8) Cases not otherwise covered X

   (e) Third Symbol—type of information to be transmitted:^2

   ^2 In this context the word “information” does not include information of a
   constant,  unvarying  nature such as is provided by standard frequency
   emissions, continuous wave and pulse radars, etc.
     (1) No information transmitted                N
     (2) Telegraphy—for aural reception            A
     (3) Telegraphy—for automatic reception        B
     (4) Facsimile                                 C
     (5) Data transmission, telemetry, telecommand D
     (6) Telephony (including sound broadcasting)  E
     (7) Television (video)                        F
     (8) Combination of the above                  W
     (9) Cases not otherwise covered               X

   (f) Type B emission: As an exception to the above principles, damped waves
   are symbolized in the Commission's rules and regulations as type B emission.
   The use of type B emissions is forbidden.

   (g) Whenever the full designation of an emission is necessary, the symbol
   for  that emission, as given above, shall be preceded by the necessary
   bandwidth of the emission as indicated in  Sec. 2.202(b)(1).

   [ 49 FR 48697 , Dec. 14, 1984]