T.50 (standard)

ITU-T recommendation T.50 specifies the International Reference Alphabet (IRA), formerly International Alphabet No. 5 (IA5), a character encoding. ASCII is the U.S. variant of that character set.

The original version from November 1988 corresponds to ISO 646. The current version is from September 1992.

History

At the beginning was the International Telegraph Alphabet No. 2 (ITA2), a five-bit code. IA5 is an improvement, based on seven-bit bytes.

• Recommendation V.3 IA5 (1968): Initial version, superseded^[1][2]
• Recommendation V.3 IA5 (1972): Superseded^[1][2]
• Recommendation V.3 IA5 (1976-10): Superseded
• Recommendation V.3 IA5 (1980-11): Superseded
• Recommendation T.50 IA5 (1984-10): Superseded^[2]
• Recommendation T.50 IA5 (1988-11-25): Superseded^[1][2]
• Recommendation T.50 IRA (1992-09-18): In force^[1][3]

Use

This standard is referenced by other standards such as RFC 3939 ("Calling Line Identification for Voice Mail Messages"). It is also used by some analog modems such as Cisco ones.^[4]

Character set

The following table shows the IA5 character set. Each character is shown with the code point of its Unicode equivalent.

IA5 character set

0

1

2

3

4

5

6

7

8

9

A

B

C

D

E

F

0x

NUL

SOH

STX

ETX

EOT

ENQ

ACK

BEL

BS

HT

LF

VT

FF

CR

SO

SI

1x

DLE

DC1

DC2

DC3

DC4

NAK

SYN

ETB

CAN

EM

SUB

ESC

FS

GS

RS

US

2x

SP

!

"

#

$

%

&

'

(

)

*

+

,

-

.

/

3x

0

1

2

3

4

5

6

7

8

9

:

;

<

=

>

?

4x

@

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

5x

P

Q

R

S

T

U

V

W

X

Y

Z

[

\

]

^

_

6x

`

a

b

c

d

e

f

g

h

i

j

k

l

m

n

o

7x

p

q

r

s

t

u

v

w

x

y

z

{

|

}

~

DEL

  Undefined, showing instead the ASCII character at that location)

  A character that, in some regions, can be combined with a previous character as a diacritic using the backspace character, which may affect glyph choice.

Standardisation

• Identical standard: ISO/IEC 646:1991 (Twinned)

See also

• ITU T.51