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.
Designation details
Bandwidth
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 modulating signal
| 0 | No modulating signal |
| 1 | One channel containing digital information, no subcarrier |
| 2 | One channel containing digital information, using a subcarrier |
| 3 | One channel containing analogue information |
| 7 | More than one channel containing digital information |
| 8 | More than one channel containing analogue information |
| 9 | Combination of analogue and digital channels |
| X | None of the above |
Type of transmitted information
Details of information
| A | Two-condition code, elements vary in quantity and duration |
| B | Two-condition code, elements fixed in quantity and duration |
| C | Two-condition code, elements fixed in quantity and duration, error-correction included |
| D | Four-condition code, one condition per "signal element" |
| E | Multi-condition code, one condition per "signal element" |
| F | Multi-condition code, one character represented by one or more conditions |
| G | Monophonic broadcast-quality sound |
| H | Stereophonic or quadraphonic broadcast-quality sound |
| J | Commercial-quality sound (non-broadcast) |
| K | Commercial-quality sound—frequency inversion and-or "band-splitting" employed |
| L | Commercial-quality sound, independent FM signals, such as pilot tones, used to control the demodulated signal |
| M | Greyscale images or video |
| N | Full-color images or video |
| W | Combination of two or more of the above |
| X | None of the above |
Multiplexing
de:Modulationsart
