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Types of radio emissions

The International Telecommunication Union uses a special system for classifying radio frequency signals. Each type of radio emission is classified according to its bandwidth, method of modulation, nature of the modulating signal, and type of information transmitted on the carrier signal.

An emission designation is of the form BBBB 123 45, where BBBB is the bandwidth of the signal, 1 is a letter indicating the type of modulation used, 2 is a digit representing the type of modulating signal, 3 is a letter corresponding to the type of information transmitted, 4 is a letter indicating the practical details of the transmitted information, and 5 is a letter that represents the method of multiplexing. The 4 and 5 fields are optional.

Table of contents
1 Designation details

Designation details


The bandwidth is expressed as three digits and a letter that occupies the position normally used for a decimal point. The letter indicates what unit of frequency is used to express the bandwidth. H indicates Hertz, K indicates kilohertz, M indicates megahertz, and G indicates gigahertz. For instance, "500H" means 500 Hz, and "2M50" means 2.5 MHz.

Type of modulation

NUnmodulated carrier
ADouble-sideband amplitude modulation (AM broadcast radio)
HSingle-sideband with full carrier (used by CHU)
RSingle-sideband with attenuated carrier
JSingle-sideband with no carrier (Shortwave utility and amateur stations)
BTwo sidebands containing different signals
CVestigial sideband (e.g. NTSC)
FFrequency modulation (FM broadcast radio)
GPhase modulation
DCombination of AM and FM or PM
PSequence of pulses without modulation
KPulse amplitude modulation
LPulse width modulation (used by WWVB)
MPulse position modulation
QSequence of pulses, phase or frequency modulation within each pulse
VCombination of pulse modulation methods
WCombination of any of the above
XNone of the above

Type of modulating signal

0No modulating signal
1One channel containing digital information, no subcarrier
2One channel containing digital information, using a subcarrier
3One channel containing analogue information
7More than one channel containing digital information
8More than one channel containing analogue information
9Combination of analogue and digital channels
XNone of the above

Type of transmitted information

NNo transmitted information
AAural telegraphy (Morse code)
BElectronic telegraphy (Radioteletype and digital modes)
CFacsimile (Still images)
DTelemetry or Telecommand (Remote control)
ETelephony (voice or audio signals)
FVideo (television signals)
WCombination of any of the above
XNone of the above

Details of information

ATwo-condition code, elements vary in quantity and duration
BTwo-condition code, elements fixed in quantity and duration
CTwo-condition code, elements fixed in quantity and duration, error-correction included
DFour-condition code, one condition per "signal element"
EMulti-condition code, one condition per "signal element"
FMulti-condition code, one character represented by one or more conditions
GMonophonic broadcast-quality sound
HStereophonic or quadraphonic broadcast-quality sound
JCommercial-quality sound (non-broadcast)
KCommercial-quality sound—frequency inversion and-or "band-splitting" employed
LCommercial-quality sound, independent FM signals, such as pilot tones, used to control the demodulated signal
MGreyscale images or video
NFull-color images or video
WCombination of two or more of the above
XNone of the above


NNone used
CCode-division (excluding spread spectrum)
WCombination of Frequency-division and Time-division
XNone of the above