47 CFR § 2.201 - Emission, modulation, and transmission characteristics.
The following system of designating emission, modulation, and transmission characteristics shall be employed.
(1) First symbol - type of modulation of the main carrier;
(2) Second symbol - nature of signal(s) modulating the main carrier;
(3) Third symbol - type of information to be transmitted.
Two additional symbols for the classification of emissions may be added for a more complete description of an emission. See Appendix 1, Sub-Section IIB of the ITU Radio Regulations for the specifications of these fourth and fifth symbols. Use of these symbols is 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):|
|- 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|
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|
|(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|
(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 § 2.202(b)(1).