Radio emissions should be expressed in a three-symbol code form, which defines the exact nature of carrier, signal and transmitted information. The first symbol defines the carrier, the second symbol defines the signal, and the third symbol defines the information.
First symbol
A Double-sideband amplitude-modulated
B Independent sideband amplitude-modulated
C Vestigial sideband amplitude-modulated
D Amplitude- and angle-modulated simultaneously, or in a
predefined sequence
F Frequency modulated
G Phase modulated
H Single-sideband, full carrier
J Single-sideband, suppressed carrier
K Amplitude-modulated pulse sequence
L Width-modulated pulse sequence
M Position phase modulated pulse sequence
N Unmodulated carrier
P Unmodulated pulse sequence
Q Pulse sequence in which carrier is angle-modulated during
the pulse period
R Single-sideband, reduced or variable level carrier V Pulse sequence with a combination of carrier modulations,
W Carrier is modulated by two or more of angle, amplitude, and pulse modes, simultaneously or in a defined sequence
X Other cases
Second symbol
0 No modulating signal
1 Digital signal without modulating sub-carrier
2 Digital signal with modulating sub-carrier
3 Analogue signal
7 Two or more channels with digital signals
8 Two or more channels with analogue signals
9 Composite system with one or more channels of digital signals and one or more channels of analogue signals X Other cases
Third symbol
A Aural telegraph
B Automatic telegraph
C Facsimile
D Data
E Telephony (and sound broadcasting)
F Television
N No information transmitted
W Combination of any of the above
X Other cases