Prentke Romich Company
http://www.prentrom.com/support/article/256
Windows 2000, XP, Vista, and Windows 7 will install the driver automatically so all you have to do is set your switch settings under the Select Menu in your Wivik Software.
Installing your USB Switch Interface Box:
After you have turned on your computer, plug the USB Switch Box into the USB port on your computer. Next you will need to install a software driver that will communicate with the USB Switch Box.
Note: If you have older Windows software please see the instructions below.
Setting up your USB Switch Interface Box:
With your Wivik program open, click on your Select menu, then click on the Scan option. This will place a check mark in front of the word Scan.
Now click on the word Options.
There are many settings available for scanning with your switch here:
Select Options from the Select menu after choosing Scan as the selection method.
It is suggested that you set scanning options in the following order.
a. Choose switch interface Connection.
Select the Game/USB options, then select PRC USB Switch Interface. Press the switch and you will see your test button blink on and off each time you press the switch.
b. Select number of Switches. 
c. Choose Method. Your options are Automatic, Inverse or Directed scanning
Scanning Methods
Automatic Scanning Methods = In automatic scanning, groups or items are automatically highlighted or scanned in sequence. The highlight pauses at each group/item for a preset time.
When you activate (press and release) the select switch, scanning begins across smaller groups or individual items. If you click the select switch when an individual item is highlighted, that item is selected. One or two switches are usually used with automatic scanning with select and cancel actions assigned to switches.
You must be able to activate the switch within the preset time to make a selection.
Inverse = With inverse scanning you advance the highlight by holding the select switch down. While the switch is held down, the highlight pauses at each item for a preset time.
Step scanning is a variation where you advance by repeatedly activating the select switch. Sometimes, step and inverse scanning are combined.
The advantage of inverse/step scanning is that timing is not as critical as with automatic scanning. Groups or items are selected with a select switch or by dwelling. Typically two or three switches are used with move, select and cancel actions assigned to switches.
Directed = Directed scanning matches separate switches with moving the highlight across individual keys. These switches are used in a step or inverse fashion.
The switches are often housed in a gated joystick, allowing users to direct the scanning cursor as they would drive an electric wheelchair. Items are selected by activating the select switch, or by dwelling for some period. Directed scanning requires the greatest degree of control.
d. Select highlighting style with Automatic and Inverse scanning.
Highlighting Styles
Row-column = Rows of items are highlighted from the top down one at a time. A selected row is then highlighted column-by-column (item-by-item) until the desired item is reached and selected. The highlighting returns to the first row after a selection.
Row-group-item = Groups of items in a selected row are highlighted until a group containing the desired item is selected. Then items within that group are highlighted until the desired item is reached and selected. The highlighting returns to the first row after a selection.
Column-row = Columns of items are highlighted one at a time. A selected column is then highlighted row-by-row (item-by-item) until the desired item is reached and selected. The highlighting returns to the first column after a selection.
Column-group-item = Groups of items in a selected column are highlighted until a group containing the desired item is selected. Then items within that group are highlighted until the desired item is reached and selected. The highlighting returns to the first column after a selection.
Quadrant scanning = The keyboard is divided into quadrants. Each quadrant is highlighted in succession. Sub-quadrants within a selected quadrant are highlighted and the process continues until individual items are highlighted.
Item scanning = Each item is highlighted one at a time, usually from left-to-right and top-to-bottom until an item is selected. After a selection, highlighting begins again with the first item and repeats scanning. Element scanning is typically limited to less than 15 items.
e. Assign specific Actions to switches. 
Automatic switch actions = For each available switch, assign an appropriate action after choosing Actions from the Scanning options dialog.
At least one switch must be defined as a Select switch. You can repeat a key by holding down he Select switch.
Select Starts scanning initially; makes selection of row/column, group, or item; repeats selection if switch is held down.
Cancel Stops scanning; control is switched to the next open WiViK keyboard when switch is activated twice in a row.
Overdrive Advances the highlight faster according to Time adjusted by the Speed Factor while switch activation is maintained.
2 Speed Toggles between scan Time and scan Time adjusted by the Speed Factor.
Move/reverse Toggles direction of scanning.
Inverse switch actions = For each available switch, assign an appropriate action after choosing from the Scanning dialog.
At least one switch must be defined as a Move-style switch. You can repeat a key by holding down the Select switch. If a Select switch is not defined, keys are automatically selected by dwelling.
Select Chooses item.
Cancel Stops scanning; control is switched to the next available scanning WiViK keyboard when switch is activated twice in a row.
Overdrive Modifies speed associated with Move switch according to Time adjusted by the Speed Factor.
Move, reverse Advances highlight when you hold the switch down or repeatedly activate the switch.
Move fast, Fast Advances highlight when you hold this switch down using the scan Time adjusted by the Speed Factor.
Move 2 speed, reverse 2 Speed Advances highlight when you hold the switch down using the standard scan Time interval until you release the switch; then when you next hold down the switch the highlight advances according to the Time adjusted by the Speed Factor; this action toggles.
Move/reverse Advances highlight when you hold the switch down until the switch is released; moves highlight in reverse direction when you next activate the switch; this action toggles.
Move/rev fast Advances highlight when you hold the switch down using the scan Time adjusted by the Speed Factor until you release the switch; moves highlight in reverse direction when you next activate the switch; this action toggles.
Directed switch actions = For each available switch, assign an appropriate action after choosing Actions from the Scanning options dialog.
At least two switches must be defined for horizontal and vertical movement. You can repeat a key by holding down the Select switch. If a Select switch is not defined, keys are automatically selected by dwelling.
Select Chooses item.
Cancel Stops scanning; control is switched to the next available WiViK keyboard when switch is activated twice in a row.
right, left, up, down Moves highlight in the switch direction when you hold the switch down or repeatedly activate the switch.
right, Fast Moves highlight in the switch direction when you hold the switch down using the scan Time adjusted by the Speed Factor.
right/left Moves highlight in the switch direction when you hold the switch down; moves highlight in the opposite direction when you next activate the switch; this action toggles.
right/left Fast up/down Fast Moves highlight in the switch direction when you hold the switch down using the scan Time adjusted by the Speed Factor until you release the switch; moves highlight in the opposite direction when you next activate the switch; this action toggles.
f. Set Timing options.
Timing settings = Timing is the most important aspect of scanning access. WiViK incorporates several timing settings that accommodate wide ranging abilities. All are based on the setting of a basic scan interval.
The following timing settings are set within each scanning strategy.
Time. This is the time interval that the highlight pauses at one location before advancing while switch activation is maintained; also, the time interval between repeating keystrokes. This should be set so that you can hit or release the switch before the highlight passes the desired row, group or item. When step scanning is used, this should be set high so that the highlight does not advance over more than one item with each hit.
This time also controls the repeat time when you hold down the select key beyond the Delay Factor. The repeat function works as follows: Delay Factor—1st selection—Delay Factor—2nd selection—Delay Factor at Scan/Repeat time.
Delay Factor. Increases the Time of the first group or item scanned by this factor. This gives you a chance to seek out the next item for selection. Typically this is set to 2.Speed Factor. Decreases the Time by this factor when using a switch defined as Overdrive, 2 Speed, or Fast. It allows you to quickly move to the approximate location of the desired row, group or item. Typically Speed Factor is set to 2 or 3. You must stop before reaching the target.
Dwell Factor. Increases the Time by this factor to dwell or wait to make a selection or to cancel scanning. If no Select switch is defined, selection is automatically set to dwelling. Cancel is only available when a Select switch is defined. Typically Factor is set to 4 or 5 for dwell selection and 6–10 for dwell canceling.
Debounce Time. The time that the user must hold down a switch to activate it. It prevents double activations of the switch caused by bouncing on the switch or poor contacts within the switch.
g. Set scanning Preferences. 
Automatic Preferences
Scanning sound. If checked, the computer beeps with every movement of the highlight.
Invisible cancel. If checked, there is an added scan interval at the end of a cycle (e.g., row) where nothing is highlighted. When the selection switch is activated, scanning stops if Scan continuously is not checked, otherwise scanning returns to the top level. (Used when a separate cancel switch is not available.)
Scan continuously. If checked, the scanning continues after any selection, otherwise scanning stops when a single item is selected.
Scan right-to-left. By default, the highlight scans left-to-right; this may be changed to right-to-left orientation.
Scan cycles. This adjusts the number of times that the highlight cycles through a group (e.g., all rows) before stopping and disappearing; if set to 0 then the highlight cycles indefinitely.
Inverse preferences
Scanning sound. If checked, the computer beeps with every movement of the highlight.
Scan right-to-left. By default, the highlight scans left-to-right; this may be changed to right-to-left orientation.
Scan cycles. This adjusts the number of times that the highlight cycles through a group (e.g., all rows) before stopping and disappearing. If set to 0 then the highlight cycles indefinitely.
Directed preferences
Scanning sound. If checked, the computer beeps with every movement of the highlight.
Scan right-to-left. By default, the highlight scans left-to-right. This may be changed to right-to-left orientation.
Select either Corner of keyboard or Center of keyboard to indicate where the highlight will start scanning.
Return to starting position after selection. If checked, the highlight returns to its starting position after every selection.
Select scan to the next line, scan the same line, or do not wrap to indicate how the highlight continues when it reaches the end of a line.
To learn how to install the USB switch interface box on a computer with Windows 98 SE or older click on the link below.
This is the installation instruction manual in pdf format.