ITU-T S.1 (03/93) / International Telegraph Alphabet No. 2

Baudot Code

Encode and decode the international ITA2 teleprinter alphabet with explicit LETTERS and FIGURES state. This is ITA2, often called Baudot-Murray code, not original Baudot/ITA1 or a US-TTY variant.

Variant International ITA2 only
Displayed bit order 54321, most significant bit first
Decode rule Explicit first shift required

01 / Encode

Text to ITA2 groups

0 / 2,000 characters

ASCII lowercase is folded to uppercase. Unsupported Unicode and unassigned characters stop encoding with a precise error.

Space is 00100. Space, CR, and LF do not change the active shift state.

Ready to encode. Every non-empty result begins with an explicit LTRS group.

0 groups

02 / Decode

ITA2 groups to text

0 / 4,096 groups

Separate every five-bit group with ASCII whitespace. The first group must be LTRS 11111 or FIGS 11011, so no starting state is guessed.

Ready to decode. Shift groups change state and do not print.

Decoded text 0 characters 

          
CR and LF are preserved as controls. NUL, WRU, and BELL are made visible as [NUL], [WRU], and [BELL].

          

            
          

        

      

    

  


  

    ITA2 code table and exact conventions
    

      

        

          Bit order
          
Groups are numeric binary values with code element 5 at left and element 1 at right. ITU serial transmission sends element 1 first, so the five displayed bits go on the wire from right to left.

        

        

          Shift state
          
LTRS 11111 selects letters and FIGS 11011 selects figures. State persists through spaces and controls until another shift arrives.

        

        

          International assignments
          
FIGURES values 01101, 10100, and 11010 are national or private positions in S.1. This tool rejects them and does not substitute !, currency signs, or &.

        

        

          Scope and limits
          
This converts five data bits only, not start and stop framing, audio RTTY, timing, or another historical alphabet. Text is limited to 2,000 characters and decoding to 4,096 groups.

        

      


      

        

          International Telegraph Alphabet No. 2, numeric display order 54321
          
            

              Group
              LETTERS
              FIGURES
            

          
          
            
00000NULNUL

            
00001E3

            
00010LFLF

            
00011A-

            
00100SpaceSpace

            
00101SApostrophe

            
00110I8

            
00111U7

            
01000CRCR

            
01001DWRU

            
01010R4

            
01011JBELL

            
01100N,

            
01101FNational/private

            
01110C:

            
01111K(

            
10000T5

            
10001Z+

            
10010L)

            
10011W2

            
10100HNational/private

            
10101Y6

            
10110P0

            
10111Q1

            
11000O9

            
11001B?

            
11010GNational/private

            
11011FIGSFIGS

            
11100M.

            
11101X/

            
11110V=

            
11111LTRSLTRS

          
        

      


      
Primary reference: ITU-T Recommendation S.1, International Telegraph Alphabet No. 2. The encoder accepts ASCII equivalents for apostrophe and hyphen. Other unsupported characters are reported, not removed.