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47 CFR §2.201

Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
The following system of designating emission, modulation, and transmission characteristics shall be employed.
  1. (a)Emissions are designated according to their classification and their necessary bandwidth.
  2. (b)Three symbols are used to describe the basic characteristics of emissions. Emissions are classified and symbolized according to the following characteristics:
    1. (1)First symbol—type of modulation of the main carrier;
    2. (2)Second symbol—nature of signal(s) modulating the main carrier;
    3. (3)Third symbol—type of information to be transmitted.
  3. (c)First Symbol—types of modulation of the main carrier:
  4. (d)Second Symbol—nature of signal(s) modulating the main carrier:
  5. (e)Third Symbol—type of information to be transmitted: 2
  6. (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.
  7. (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).