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From: andyb@coat.com (Andy Behrens)
Newsgroups: comp.dcom.telecom
Subject: Re: The 'Public Telegraph Office'
Message-ID: 
Date: 3 Oct 89 04:54:24 GMT
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X-TELECOM-Digest: volume 9, issue 425, message 6 of 6

Dik T. Winter  writes:
> Here follows the CCITT #2 code table:
>
>	Letters					Figures
>	0	8	16	24
>    +--------------------------------------------------------
> 0  |	space	LF	E	A		...
> 1  |	T	L	Z	W		...
> 2  |	CR	R	D	J		...
> 3  |	O	G	B	figures		...
> 4  |	nil	I	S	U		...
> 5  |	H	P	Y	Q		...
> 6  |	N	C	F	K		...
> 7  |	M	V	X	letters		...

At first there seems to be no pattern to the way the letters are
assigned, but if you arrange them according to the number of bits that
are set in each character, it becomes clear.  The most common letters
of the English alphabet (ETAIONSHRDL....) and the word separators
(space, return, line feed) have the codes with the fewest number of
marking bits.

Question 1.  Does anyone know why this is so?

    My theory: If the teletype machines are driven with a current-loop
    interface, this arrangement of codes minimizes the power that needs
    to be transmitted.

Question 2.  Why was "Z" grouped with the most common letters?

============ ============ ============ ============ ============ ============
 no bits      1 bit        2 bits       3 bits       4 bits       5 bits
============ ============ ============ ============ ============ ============
00000 blank  10000 E      11000 A      01110 C      11110 K      11111 ltrs
             01000 lf     01100 I      10110 F      11101 Q
             00100 space  00110 N      01101 P      11011 figs
             00010 ret    00011 O      11010 J      10111 X
             00001 T      10100 S      10101 Y      01111 V
                          01010 R      01011 G
                          00101 H      11100 U
                          10010 D      11001 W
                          01001 L      10011 B
                          10001 Z      00111 M
============ ============ ============ ============ ============ ============


Live justly, love gently, walk humbly.
					Andy Behrens
					andyb@coat.com

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