47 C.F.R. § 2.302
The table which follows indicates the composition and blocks of international call signs available for assignment when such call signs are required by the rules pertaining to particular classes of stations. When stations operating in two or more classes are authorized to the same licensee for the same location, the Commission may elect to assign a separate call sign to each station in a different class. (In addition to the U.S. call sign allocations listed below, call sign blocks AAA through AEZ and ALA through ALZ have been assigned to the Department of the Army; call sign block AFA through AKZ has been assigned to the Department of the Air Force; and call sign block NAA through NZZ has been assigned jointly to the Department of the Navy and the U.S. Coast. Guard.
| Class of station | Composition of call sign | Call sign blocks |
| Coast (Class I) except for coast telephone in Alaska | 3 letters | KAA through KZZ. WAA through WZZ. |
| Coast (Classes II and III) and maritime radio-determination | 3 letters, 3 digits | KAA200 through KZZ999. WAA200 through WZZ999. |
| Coast telephone in Alaska | 3 letters, 2 digits | |
| 3 letters, 3 digits (for stations assigned frequencies above 30 MHz) | KAA20 through KZZ99. WAA20 through WZZ99. WZZ200 through WZZ999. | |
| Fixed | 3 letters, 2 digits 3 letters, 3 digits (for stations assigned frequencies above 30 MHz) | KAA20 through KZZ99. WAA20 through WZZ99. WAA200 through WZZ999. |
| Marine receiver test | 3 letters, 3 digits (plus general geographic location when required) | KAA200 through KZZ999. WAA200 through WZZ999. |
| Ship telegraph | 4 letters1 | KAAA through KZZZ. WAAA through WZZZ. |
| Ship telephone | 2 letters, 4 digits, or 3 letters, 4 digits1 | WA2000 through WZ9999, through WZZ9999. |
| Ship telegraph plus telephone | 4 letters | KAAA through KZZZ. WAAA through WZZZ. |
| Ship radar | Same as ship telephone and/or telegraph call sign, or, if ship has no telephone or telegraph: 2 letters, 4 digits, or 3 letters, 4 digits | WA2000 through WZ9999, through WZZ9999. |
| Ship survival craft | Call sign of the parent ship followed by 2 digits | KAAA20 through KZZZ99. WAAA20 through WZZZ99. |
| Cable-repair ship marker buoy | Call sign of the parent ship followed by the letters "BT" and the identifying number of the buoy | |
| Marine utility | 2 letters, 4 digits | KA2000 through KZ9999. |
| Shipyard mobile | 2 letters, 4 digits | KA2000 through KZ9999. |
| Aircraft telegraph | 5 letters | KAAAA through KZZZZ. WAAAA through WZZZZ. |
| Aircraft telegraph and telephone | 5 letters2 | KAAAA through KZZZZ. WAAAA through WZZZZ. |
| Aircraft telephone | 5 letters2 (whenever a call sign is assigned) | KAAAA through KZZZZ. WAAAA through WZZZZ. |
| Aircraft survival craft | Whenever a call sign2 is assigned, call sign of the parent aircraft followed by a single digit other than 0 or 1 | |
| Aeronautical | 3 letters, 1 digit2 | KAA2 through KZZ9. WAA2 through WZZ9. |
| Land mobile (base) | 3 letters, 3 digits | KAA200 through KZZ999. WAA200 through WZZ999 |
| Land mobile (mobile telegraph) | 4 letters, 1 digit | KAAA2 through KZZZ9. WAAA2 through WZZZ9. |
| Land mobile (mobile telephone) | 2 letters, 4 digits | KA2000 through KZ9999. WA2000 through WZ9999 |
| Broadcasting (standard) | 4 letters3 (plus location of station) | KAAA through KZZZ. WAAA through WZZZ. |
| Broadcasting (FM) | 4 letters (plus location of station) | KAAA through KZZZ. WAAA through WZZZ. |
| Broadcasting with suffix "FM" | 6 letters3 (plus location of station) | KAAA-FM through KZZZ--FM. WAAA-FM through WZZZ-FM. |
| Broadcasting (television) | 4 letters (plus location of station) | KAAA through KZZZ. WAAA through WZZZ. |
| Broadcasting with suffix "TV" | 6 letters3 (plus location of station) | KAAA-TV through KZZZ-TV. WAAA-TV through WZZ-TV. |
| Television broadcast translator | 1 letter-output channel number-2 letters | K02AA through K83ZZ. W02AA through W83ZZ. |
| Disaster station, except U.S. Government | 4 letters, 1 digit | KAAA2 through KZZZ9. WAAA2 through WZZZ9. |
| Experimental (letter "X" follows the digit) | 2 letters, 1 digit, 3 letters | KA2XAA through KZ9XZZ. WA2XAA through WZ9XZZ. |
| Amateur (letter "X" may not follow digit) | 1 letter, 1 digit, 1 letter4 | K1A through K0Z. N1A through N0Z. W1A through W0Z. |
| Amateur | 1 letter, 1 digit, 2 letters4 | K1AA through K0ZZ. N1AA through N0ZZ. W1AA through W0ZZ. |
| Do | 1 letter, 1 digit, 3 letters4 | K1AAA through K0ZZZ. N1AAA through N0ZZZ. W1AAA through W0ZZZ. |
| Do | 2 letters, 1 digit, 1 letter4 | AA1A through AI0Z. KA1A through KZ0Z. NA1A through NZ0Z. WA1A through WZ0Z. |
| Do | 2 letters, 1 digit, 2 letters4 | AA1AA through AL0ZZ. KA1AA through KZ0ZZ. NA1AA through NZ0ZZ. WA1AA through WZ0ZZ. |
| Amateur (letter "X" may not follow digit) | 2 letters, 1 digit, 3 letters4 | AA1AAA through AL0ZZZ. KA1AAA through KZ0ZZZ. NA1AAA through NZ0ZZZ. WA1AAA through WZ0ZZZ. |
| Standard frequency | WWV, WWVB through WWVI, WWVL, WWVS. | |
| Personal radio | 3 letters, 4 digits, or 4 letters, 4 digits. | KAA0001 through KZZ9999, WAA0001 through WPZ9999, KAAA0001 through KZZZ9999. |
| Personal radio, temporary permit | 3 letters, 5 digits | KAA00000 through KZZ99999. |
| Personal radio in trust territories. | 1 letter, 4 digits | K0001 through K9999. |
| Business radio temporary permit | 2 letters, 7 digits | WT plus local telephone number. |
| Part 90 temporary permit | 2 letters, 7 digits | WT plus local telephone number. |
| Part 90 conditional permit | 2 letters, 7 digits | WT plus local telephone number. |
| General Mobile Radio Service, temporary permit | 2 letters, 7 digits | WT plus business or residence telephone number. |
NOTE: The symbol 0 indicates the digit zero.
1 Ships with transmitter-equipped survival craft shall be assigned four letter call signs.
2 See § 2.303 .
3 A 3 letter call sign now authorized for and in continuous use by a licensee of a standard broadcasting station may continue to be used by that station. The same exception applies also to frequency modulation and television broadcasting stations using 5 letter call signs consisting of 3 letters with the suffix "FM" or "TV".
4 Plus other identifying data as may be specified.
47 C.F.R. §2.302
For Federal Register citations affecting §2.302, see the List of CFR Sections Affected, which appears in the Finding Aids section of the printed volume and at www.fdsys.gov.