WARC-79, the World Administrative Radio Conference that rewrote many
of the world's radio regulations, adopted a new system of emission
classification.  The traditional A (Amplitude), F (Frequency), and P
(Pulse) was intuitive, but limited and clumsy when dealing with new
modes.

The world's radio bodies, including the FCC, gradually phased in the
new system until today it completely replaces the old one.

The formula for the new designations, loosely from ITU radio
regulations 264 through 273, and Appendix 6, Part A, is:

[BBBB]MNI[DM],

where

[] means optional when writing emission specs.


[BBBB] = Necessary Bandwidth (shown in FCC records, but is often
      omitted elsewhere)

Uses a letter and three numbers.  The letter goes where the decimal
point should be placed, and denotes a magnitude:

H        Hz
K        kHz
M        MHz
G        GHz

Some common bandwidths are:

400 Hz     400H
2.4 kHz    2K40
12.5 kHz   12K5
6 MHz      6M00



M = Modulation Type

N   None
A   AM (Amplitude Modulation), double sideband, full carrier
H   AM, single sideband, full carrier
R   AM, single sideband, reduced or controlled carrier
J   AM, single sideband, suppressed carrier
B   AM, independent sidebands
C   AM, vestigial sideband  (commonly analog TV)

F   Angle-modulated, straight FM
G   Angle-modulated, phase modulation (common; sounds like FM)

D   Carrier is amplitude and angle modulated

P   Pulse, no modulation
K   Pulse, amplitude modulation (PAM, PSM)
L   Pulse, width modulation (PWM)
M   Pulse, phase or position modulation (PPM)
Q   Pulse, carrier also angle-modulated during pulse
W   Pulse, two or more modes used

X   All cases not covered above


N =  Nature of modulating signal

0   None
1   Digital, on-off or quantized, no modulation
2   Digital, with modulation
3   Single analog channel
7   Two or more digital channels
8   Two or more analog channels
9   Composite, one or more digital channel, one or more analog

X   All cases not covered above


I = Information type

N   None
A   Aural telegraphy, for people (Morse code)
B   Telegraphy for machine copy (RTTY, fast Morse)
C   Analog fax
D   Data, telemetry, telecommand
E   Telephony, voice, sound broadcasting
F   Video, television
W   Combinations of the above

X   All cases not covered above


[DM] = additional details, not used by FCC, optional elsewhere

D = Detail


RTTY/modems:

A   Two condition code, differing numbers or durations (Morse)
B   Two condition code, same number and duration, no error check
C   Two condition code, same num & dur, error check
D   Four condition code, 1 or more bits per condition
E   Multi condition code, 1 or more bits per condition
F   Multi condition code, conditions may combine

Audio:

G   Broadcast quality (mono)
H   Broadcast quality (stereo/multichannel)
J   Commercial quality
K   Commercial quality, analog freq inversion or band scrambling
L   Commercial quality, FM pilot tone (i.e. Lincomprex)

Video:

M   Monochrome
N   Color


W   Combination

X   All cases not covered above



M = Multiplex type

N   None
C   Code division
F   Frequency division
T   Time division
W   Combination of above

X   All other types



-----------------------------------------------------------------------


            Converting Between Old & New Systems


-----------------------------------------------------------------------


USE                           OLD                 NEW

Pure carrier                  A0,F0               N0N
Morse telegraphy (by ear)     A1                  A1A
Modulated CW Morse            A2                  A2A
AM voice                      A3                  A3E
SSB, suppressed carrier       A3J                 J3E
SSB, reduced carrier          A3R                 R3E
SSB, full carrier             A3H                 H3E
Television                    A5                  C3F

RTTY (F.S.K.)                 F1                  F1B
RTTY        (A.F.S.K.)        F2                  F2B
FM voice (Narrowband)         F3                  F3E, 20K0F3E


Packet Data/Teleprinters
with Audio Sub-Carrier      20F2                20K0F2B

Data with Audio Sub-carrier    3F2                3K00F2D
                            6F2                6K00F2D
                           20F2                20K0F2D

Analog Voice                  20F3                20K0F3E

Digital Voice                 20F3Y               20K0F1E

Digital Facsimile without
Audio Sub-Carrier           20F4                20K0F1C

Digital Facsimile with
Audio Sub-Carrier           20F4                20K0F2C

Analog Facsimile              20F4                20K0F3C

Composite of Digital &
Analog Information           3F9                3K00F9W
                            6F9                6K00F9W
                           20F9                20K0F9W

Packet Data/Teleprinters
without Audio Sub-Carrier   20F9Y               20K0F1B

Digital Data                  20F9Y               20K0F1D



LAND MOBILE EMISSIONS               MICROWAVE EMISSIONS
old      new       old    new       old       new
A0      N0N       P0     P0N        F9       F8W (If bw is less than
A1      A1A       P9     P0N                      50 convert to F2D)
A3      A3E       A2J    J2B        F9Y      F7W (If bw is less than
A3J     J3E       A3H    H3E                      50 convert to F2D)
A7J     J8W       A9J    J9W        F3       F3E
A9      A9W       P1     P1D        A9Y      A7W
A9Y     A1D       F2Y    F2D        A5       A3F
F0      N0N       A0H    H0N        A9       A8W
F1      F1B       A7     A8D        A5C      C3F
F2      F2D       F7     F8D        F2       F2D
F3      F3E                         F5       F3F
F3Y     F1E
F4      F3C
F9      F9W
F9Y     F1D
A2H     H2D
A2      A2D


----------------------------------------------------------------------

And here is the relevant section of FCC rules:

----------------------------------------------------------------------




                 From General Docket No. 80-739

Section 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 carrier;

  (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:*
       - 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, a combination of two  or
       more of the following modes:  amplitude, angle, pulse      W

  (7)  Cases not otherwise covered                                X

  *Emissions where the main carrier is directly modulated by a
  signal  which  has been coded into  quantizied  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 multiplex                 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, to-gether with one or
       more channels containing analogue information              9

  (8)  Cases not otherwise covered                                X

(e)  Third Symbol - type of information to be transmitted:

  (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 Section 2.202 (b) (1).


Section 2.202 Bandwidths.

(b)   Necessary bandwidths.

  (1)  The  necessary  bandwidth shall be expressed  by  three
       numerals  and  one  letter.  The  letter  occupies  the
       position  of the decimal point and represents the  unit
       of  bandwidth.   The first character shall  be  neither
       zero nor K, M or G.