Input/Output Modalities CSD 823X Spring 2011 John B. Eulenberg, Professor

Three Input Modes Direct Selection Encoding Scanning –Serial Scanning –Directed Scanning –Single-Switch vs. Double-Switch –Row-and-Column Scanning

Definition: Language Space The spatial arrangement of the terminal symbols of the universe of linguistic elements at any one level of linguistic abstraction Examples: –Vowel space in the oral cavity –Letters on a keyboard –Word-squares on a language board –The 7 keys on the BAT chordic keyboard

“Terminal Symbols” The ultimate symbols that one uses to construct an utterance. Examples: –Phonemes –Letters –Pictures or Pictograms –Switch-Chords on a chordic keyboard

Direct Selection Direct Selection pertains to a language space where all the ultimate units are accessible. This is usually a rather large set of symbols Examples: –Computer Keyboard accessed by hand-finger movement (typical “normal” access) –Squares on a touch screen (e.g. DynaVox) accessed by head stick –Joystick with separate individual rest places (detented joystick) –Language board accessed by hand/finger pointing –Eye gaze at a large number of symbols

Encoding Encoding is used when the communicating person can hit a few items (not just one, but not a lot) at a time. Examples: –Morse Code (where one chooses one of TWO items) –Eugene Chernyakhovsky’s language board, where the periphery presented the numbers from 0 to 9, and each item was encoded with an index number from 0 to 999 (see “Eugene”) –Julie Hastings’s hand control, with which shiactivated one of six switches, in pairs, so she could point to one of 36 items.

Julie Hastings System Julie’s fingers map in pairs of numbered switches to one of 36 cells =A, 1-2=B,…3-4=L...

Scanning Used primarily when the number of items that can be accessed at any time is just two (on/off, hit switch or not hit switch, blink or not blink) A binary choice is made as items are presented by another person or by a device

Serial Scanning In serial scanning, items are presented one after another, from first to last. Example: –Presenting the alphabet as ‘A, B, C,….X, Y,Z’ to a person, waiting for the person to squeeze your hand when you get to the letter she/he wishes to add.

Average Cost for Getting A Letter (in time units) Serial Scanning Letters Average Letter will take 13 time units Minimum is 1 Maximum is 26

Most Frequent Letters in English Text: ETAOIN SHLDRU

Row-and-Column Scanning Items are arranged in rows User first selects a row, as rows are presented in sequence User then selects the item in a row (column select)

Cost of Getting a letter in a Row and Column Arrangement Five Rows, So average cost of row is 2.5 units. Five Columns, so average cost to get to item is 2.5. Maximum cost (YZ) is 10 Average Cost to get to a letter 5 Minimum Cost (A) is 2

Directed Scanning This is half-way between a direct-access joystick and row-and-column scanning. The user is more “in control” than in row- and-column scanning, but it is slower than a direct-access joystick. In Directed Scanning, you use a joystick to indicate the direction of the scan, while the items are scanned one-by-one.

Single-Switch vs. Double-Switch Single-Switch Scanning: The switch is used both for choosing rows and columns Double-Switch Scanning: –Switch 1 is used for advancing the cursor –Switch 2 is used for activating the current choice (whether row or item in row)