Aeronautical Information Manual (AIM), page 191
5/26/16 12/10/15 AIM 2. Telephone users. When using the telephone press 1, 2, or 3, depending upon whether the letter you to make a reservation, you are prompted for input of desire is the first, second, or third letter on that key. information about what you wish to do. All input is For example to enter the letter "N" first press the accomplished using the keypad on the telephone. The "6" key because "N" is on that key, then press the only problem with a telephone is that most keys have "2" key because the letter "N" is the second letter on a letter and number associated with them. When the the "6" key. Since there are no keys for the letters "Q" system asks for a date or time, it is expecting an input and "Z" e-CVRS pretends they are on the number of numbers. A problem arises when entering an "1" key. Therefore, to enter the letter "Q", press 11, aircraft call sign or tail number. The system does not and to enter the letter "Z" press 12. detect if you are entering a letter (alpha character) or NOTE- a number. Therefore, when entering an aircraft call Users are reminded to enter the "N" character with their sign or tail number two keys are used to represent tail numbers. (See TBL 4-1-4.) each letter or number. When entering a number, 3. For additional helpful key entries, see precede the number you wish by the number 0 (zero) TBL 4-1-5. i.e., 01, 02, 03, 04, . . .. If you wish to enter a letter, first press the key on which the letter appears and then TBL 4-1-4 Codes for Call Sign/Tail Number Input Codes for Call Sign/Tail Number Input Only A-21 J-51 S-73 1-01 B-22 K-52 T-81 2-02 C-23 L-53 U-82 3-03 D-31 M-61 V-83 4-04 E-32 N-62 W-91 5-05 F-33 O-63 X-92 6-06 G-41 P-71 Y-93 7-07 H-42 Q-11 Z-12 8-08 I-43 R-72 0-00 9-09 TBL 4-1-5 Helpful Key Entries # After entering a call sign/tail number, depressing the "pound key" (#) twice will indicate the end of the entry. *2 Will take the user back to the start of the process. *3 Will repeat the call sign/tail number used in a previous reservation. *5 Will repeat the previous question. *8 Tutorial Mode: In the tutorial mode each prompt for input includes a more detailed description of what is expected as input. *8 is a toggle on/off switch. If you are in tutorial mode and enter *8, you will return to the normal mode. *0 Expert Mode: In the expert mode each prompt for input is brief with little or no explanation. Expert mode is also on/off toggle. Services Available to Pilots 4-1-19
Page 191 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures