|
|
|
|
|
|
|
Standard Telex Crypto MTK-2 → ITA-5 →
Baudot-Murray code
In digital telegraphy (teleprinter, telex)
a 5-bit encoding standard is commonly
used to represent a character (letter, number or punctuation mark).
Although this code is generally known as the Baudot code,
this name is actually wrong.
The official name for the latest telegraphy standard
is ITA-2 (International Telegraph Alphabet No 2).
It was superceeded by ITA-5 (ASCII) in 1963,
but is still used by amateurs today.
The most common 'Baudot' code is also known as Murray code, or as
Baudot-Murray code. The ITA-2 standard is used widely with
historical cipher machines.
Normal text consists of over 50 different characters (26 letters,
10 numbers, 10 punctuation marks and some control codes).
In the ITA-2 standard, 5 bits are used to represent a character, which
means that only 32 different codes can be created (25).
As this would not be sufficient for normal text, most codes
are used twice (i.e. have two different meanings) and special
reserved codes
are used to shift between the two code sets,
known as Letters (LTRS) and Figures (FIGS).
The table below shows the interpretation of the commonly used ITA-2
standard. Although this code has officially been superceeded by
ITA-5,
it is still used today on some old telex networks and by Radio Amateurs.
Some of the cipher machines described on this website,
use 5-bit digital encoding and many of them
(if they support the Latin character set) follow the ITA-2 standard.
LTRS-shift is represented by 111·11 (5 holes), so that it can be
used to wipe part of a paper tape, without affecting the rest.
Normally, a paper tape would start with two LTRS characters, to ensure
that the teletype is in Letters-mode.
By convention, the holes (bits) in the tape are called channels
or tracks and the tape is shown as it would run through the reader
away from you.
|
|
|
Cipher machines that use ITA-2
|
|
|
|
Ltr
|
Letters (A-Z)
|
|
Fig
|
Figures (Numbers and punctuation marks)
|
|
Ctrl
|
Control characters
|
|
Hex
|
Hexadecimal code
|
|
Bin 1
|
Binary, Positions of the holes in the paper tape
|
|
|
#
|
Ltr
|
Fig
|
Hex
|
Bin
|
|
|
|
|
0
|
NUL
|
00
|
000·00
|
NULL, Nothing (blank tape)
|
|
1
|
E
|
3
|
01
|
000·01
|
|
|
2
|
LF
|
02
|
000·10
|
Line Feed (new line)
|
|
3
|
A
|
-
|
03
|
000·11
|
|
|
4
|
SP
|
04
|
001·00
|
Space
|
|
5
|
S
|
'
|
05
|
001·01
|
|
|
6
|
I
|
8
|
06
|
001·10
|
|
|
7
|
U
|
7
|
07
|
001·11
|
|
|
8
|
CR
|
08
|
010·00
|
Carriage Return
|
|
9
|
D
|
ENC
|
09
|
010·01
|
Enquiry (Who are you?, WRU)
|
|
10
|
R
|
4
|
0A
|
010·10
|
|
|
11
|
J
|
BEL
|
0B
|
010·11
|
BELL (ring bell at the other end)
|
|
12
|
N
|
,
|
0C
|
011·00
|
|
|
13
|
F
|
!
|
0D
|
011·01
|
Can also be %
|
|
14
|
C
|
:
|
0E
|
011·10
|
|
|
15
|
K
|
(
|
0F
|
011·11
|
|
|
16
|
T
|
5
|
10
|
100·00
|
|
|
17
|
Z
|
+
|
11
|
100·01
|
|
|
18
|
L
|
)
|
12
|
100·10
|
|
|
19
|
W
|
2
|
13
|
100·11
|
|
|
20
|
H
|
$
|
14
|
101·00
|
Currency symbol — Can also be £
|
|
21
|
Y
|
6
|
15
|
101·01
|
|
|
22
|
P
|
0
|
16
|
101·10
|
|
|
23
|
Q
|
1
|
17
|
101·11
|
|
|
24
|
O
|
9
|
18
|
110·00
|
|
|
25
|
B
|
?
|
19
|
110·01
|
|
|
26
|
G
|
&
|
1A
|
110·10
|
Can also be @
|
|
27
|
FIGS
|
1B
|
110·11
|
Figures (Shift on)
|
|
28
|
M
|
.
|
1C
|
111·00
|
|
|
29
|
X
|
/
|
1D
|
111·01
|
|
|
30
|
V
|
;
|
1E
|
111·10
|
|
|
31
|
LTRS
|
1F
|
11·111
|
Letters (Shift off)
|
|
|
|
|
|
Any links shown in red are currently unavailable.
If you like the information on this website, why not make a donation?
© Crypto Museum. Created: Tuesday 20 January 2015. Last changed: Tuesday, 28 February 2023 - 08:45 CET.
|
 |
|
|
|
| |
