🚀 go-pugleaf

I have been reading the previous discussions about chord keyboards with great
interest. In a sense, the term chord keyboard has been misused in this group. 
There have been a number of "one-handed keyboards" proposed and built. Only
two that I know of qualify as "chord" keyboards. A chord is defined as pressing
multiple keys simultaneously which produce a STRING of characters. This is very
different from the MicroWriter keyboard or the ASCII Ball keyboard which
require pressing multiple keys to get ONE character. The stenographer keyboard 
mentioned in an earlier article has the operater press multiple keys 
simultaneously to produce shorthand characters which represent a phonetic
symbol. This meant that a word takes as many strokes as there are phonetic
syllables. Since this number is less than the number of letters in a word, this
keyboard has been called a chord keyboard. 

In the mid seventies, work went on at IBM to develop a one-handed keyboard they
called the "Chord Keyboard" (patented and trademarked!). This keyboard was
a remarkable step forward in one-handed typing. The keyboard was made up of
a five-by-two array of square keys operated by the fingers and a row of four
rectangular keys operated by the thumb. The finger keys had rounded depressions
called dimples. Each square key had a dimple in the center, half a dimple on
each side, and a quarter of a dimple on each corner. Thus a dimple was formed
at the intersection of two side by side keys, as well as the intersection of 
four keys arranged in a square. Each type of dimple produced different tactile
feedback as pressing a center dimple involved pressing one key, pressing a side
dimple involved pressing two keys and pressing a corner dimple involved 
pressing four keys. The innovation of overlaying dimples at the intersection of
keys meant that far fewer keys are necessary and the "travel distance" of the
finger is much shorter. The thumb keys had "troughs" instead of dimples, and
one can press either one thumb key (center trough) or two adjacent thumb keys 
(side troughs). There is a finger dimple for every letter and number. The thumb
troughs controlled UPPERCASE, UPPER-LOW, SPECIAL (!#$%* etc.), SPACE, 
REVERSE and others.

Since finger keys are used for different meanings depending on which dimple is 
pressed, some possible combinations of letters are not available in a single
chord. IBM did a great deal of research into digrams and trigrams (two and
three character combinations) encountered in legal, technical and general 
literature. The keyboard layout was arrived at by running massive amounts 
of text through layout simulators which measured average number of characters
per chord and finger distance travelled, amoung other things. They also 
did studies on which combination of finger motion is most reliable in humans
(ie which "chords" on a five key keyboard could be pressed the fastest with
the most accuracy by untrained individuals). This was also fed into the 
simulator so only "favorable" chords were allowed. For example, most people
find that pressing thier middle finger and pinky at the same time is difficult
if the fourth finger isn't pressed as well.

The final layout consisted of common constenants on the left and vowels on the
right dimples. For example the characters "the", "tho", "ing",
and "er", are all one chord. This is what makes the chord keyboard so 
efficient.

One particularly innovative feature was in the use of the thumb keys to 
modify finger chords. The most common character in the english language is
the space character. This was assigned to a thumb key so that it could be typed
in conjunction with any finger chord. Thus, the characters " the", is also one
chord. Pressing UPPER with "the" produced "THE". Pressing UPPER-LOW with "the"
produced "The". And pressing the trough between SPACE and UPPER-LOW along with
"the" produced " The"! REVERSE would change "le" to "el".
A typical sentenced would be typed:

	/In/ thi/s/ se/g/me/nt/ of/ te/xt/ the/ cho/rd/ bo/und/ar/i/es/ ha/ve/
	be/en/ s/ho/wn/ by/ li/ne/s/.

I trained on the chord keyboard for about three months in 1978 and was able
to type between 45 and 50 words a minute. I used the chord keyboard for the
rest of the year to do all my memos, reports and software input. I found
that parsing sentences into chords became a very natural exercise.
Interestingly, most people learned
to type with their "weak" hand (ie right-handers used their left hand to type).
This meant your normal writing hand was free to jot notes or turn pages!

Since many of the chords that could be pressed made no sense, (pressing REVERSE
and a single character for example), many chords were available for special
things. A list of dozens of common english words were available through
special chords like "this that them for have had could would" etc. In fact,
the entire kanji charater set can be mapped to the chord keyboard!

References:
"The Chord Keyboard" - Nathaniel Rochester and Frank Bequaert
	December 1978 IEEE COMPUTER

"Chord Keyboard Architecture" - Nathaniel Rochester and Frank Bequaert
	1978 IBM Poughkeepsie Laboratory Tech. Report

"One-handed Chord Keyboard And Its Control Means" - Frank Bequaert and
	Nathaniel Rochester, US PATENT 4,042,777 issued Aug 16, 1977.



Cheers, Jamie Riotto
UNISYS
(408) 435-3785
convergent.com!risky!jamie