Bert Shire, John McAlpine, Linda Petty, Chris Ridpath, Larry Silver, Ed Snell Bloorview Children's Hospital
Willowdale, Ontario, CANADA


For individuals with progressive degenerative disorders technology reduces the effect of disability on active and vital lifestyles. As more and more pieces of technology are added to an individual's system it is important that an overall perspective of the client, their needs, and their existing technology be considered. A smooth integration of new and existing technology can increase the functionally and potential of the entire system. This paper describes the prescription and integration of a computer access system with powered mobility, powered tilt system, portable ventilator, and environmental control.


John is twenty four years old, has a diagnosis of Duchehenne's Muscular Dystrophy and has required full time ventilation for the past six years. He uses powered mobility, has interests in vocational pursuits and enjoys recreational reading. Formally an inpatient of Bloorview Children's Hospital, John is currently living in an apartment supported by attendant care services and assistive devices.

The powered mobility system is based upon an Invacare Arrow with an MCC MK III controller and 1551 switch option interface. The Roho seating is incorporated into a TARSYS tilt-in-space system with a QUAX interface. The QUAX allows the use of a single input switch to alternately control UP and DOWN movement of the tilt-in-space system. The tilt-in-space system provides independent pressure relief controlled through a low force (.98 Newtons) microswitch accessed by John's right thumb. Careful consideration was given to mounting a portable ventilator (1)(2) on the powered wheelchair. The mobility system was supplied in 1993.

Dual modes of control for the powered mobility system were provided through a short throw joystick and a sip and puff interface. Originally the sip and puff interface was intended to be used when fatigue and cold temperatures prevented use of the short throw joystick. Latched sip and puff, adjusted for the most sensitive pneumatic levels, has now become the exclusive access method for mobility. A second low force microswitch (mounted adjacent to the tilt-in space microswitch and also accessed by the right thumb) was provided to select modes on the MCC controller. These modes are STANDBY, DRIVE A DRIVE B, SPEED 1, SPEED 2, SPEED 3, and ECU 1 and are stepped through sequentially each activation of the microswitch. DRIVE A and DRIVE B were setup to represent short throw joystick and pip and puff control schemes respectively.

ECU l on the MCC controller provides four dry contact relay outputs with a common ground. Each the relay outputs can be selected by respective activations of the mobility interface s FWD, REV LEFT and RIGHT directions. Two of the outputs were used to control a two channel Stanley door transmitter which John used to open his apartment door and apartment building front door. The other two outputs were used to control the Bloorview Wireless Switch Link transmitter. The Bloorview Wireless Switch link is a dual channel, radio frequency, transmitter/receiver set which provides wireless switch access to stationary equipment. In John's case this accessed the CHEC 2 (3) integrated environmental control system and allowed him control his home entertainment equipment, telephone and other devices involved in daily living. A Bloorview Battery Adaptor (4) converts the 24 volt wheelchair batteries into three independently adjustable voltages. Two of these voltages powers the Stanley door transmitter and the Wireless Switch Link to eliminate the need for disposable batteries.

For written communication John had used a series adaptive devices that changed as his needs increased and his physical abilities declined. His first computer, an IBM AT was initially accessed through the keyboard and a hand held pencil. As range movement and fatigue became a problem, the Bloorview Mini-keyboard (5) was developed for John' This was a small, 7" x 2 1/2", keyboard based on the Sharp PC-1360 Pocket Computer, requiring only grams of force to activate the keys. John acquired donated Amiga computer in 1989 for graphics and game use. His functional range of movement and available strength had decreased to the point however where the Mini-keyboard no longer could meet h needs. The technologist and programmer at Bloorview Children's hospital adapted the Amiga to accept two switch mouse cursor control and Morse code character input John continued to use this computer until his move to an attendant care apartment two years ago.

John's mobility and environmental control systems continue to "evolve' with his changing needs. Most ,recently his needs have been directed towards desk top publishing as a vocational goal and the tools necessary for this achievement. John requested the Writing Aid Clinic at Bloorview Children's Hospital to review his personal writing aid needs.


There was the presence of bilateral elbow flexion contractures in the left arm of 105 degrees and right arm of 90 degrees. Wrist flexion contractures were also present with a left wrist flexion contracture of 105 degrees and right wrist of 95 degrees which restricted functional hand use. Bilateral arm troughs had been provided to stabilize the elbows and forearms. Any movement against gravity was difficult for John.

It was decided to try a Macintosh based system with john. A wide range of commercial software specific to John's educational and career goals was available for the Macintosh. Several options for the alternate access required by John were also available. Ke:nx operating as the single switch Morse input device was chosen as the alternate access method because of John's pervious experience with Morse code. A TASH mouse emulator to provide on screen cursor control through John's wheelchair ECU output was obtained and the system assembled for trials.

John had functional use of both his right thumb and his left little finger being able to exert forces of .49 and .61 Newtons respectively. The right thumb was already operating his wheelchair seating tilt system and his wheelchair controller mode select functions through two low force microswitches. A third low force microswitch was placed beside and anterior to the first and second switches. This was however at the extreme functional range of John's right-hand thumb. fatigue would quickly set in given the thumb extension required to reach the switch and the high number of separate activations needed to input Morse. John s left hand and specifically his left little finger was now free for other functions with the recent switch to sip and puff for wheelchair control The available force of .61 Newtons was enough to operate low torque microswitch. It was anticipated however that fatigue would still be a problem given the number of activations needed to generate Morse code. A capacitive touch switch which has the characteristics of zero travel to activate and near zero Contact force (6) was chosen as the Morse input switch to help minimize fatigue. The capacitive touch switch plugged directly into the Ke:nx hardware box and the Ke:nx Morse code software setup was loaded as the Macintosh power on configuration.

The second ECU output of the Arrow wheelchair controller was enabled. A custom 9 pin cable was constructed to connect the ECU 2 outputs to the TASH Mouse Emulator providing John mouse cursor movement control through his wheelchair sip and puff control system. The "Mouse Select" was activated by the third microswitch accessed by John's right thumb and its output tied into the 9 pin cable.

Sip and puff control of the mouse proved to be a problem during training. John experienced difficulty in maintaining the "hard" puff needed to move the mouse's cursor up screen. There was also the combined effect of using the wheelchair sip and puff control with the TASH mouse emulator a combination which produced on screen mouse movements too coarse for easy control. Intended targets were overshot and considerable cursor repositioning was required.

At this point it was decided to try the Bloorview Mini Morse (7) for mouse emulation through the touch switch inputting of Morse code control sequences (7). This would be a less direct method of mouse cursor control than using the directional ECU 2 outputs 1 did prove to provide better control of the cursor due to the Mini Morse's ramped speed mouse cursor movement.

Morse input to Ke:nx had also proved to be a problem as the Morse code speed adjustment was not fine enough to meek John's needs The Mini Morse was also be able to emulate the Macintosh keyboard directly from the Morse coded character input stream (from the capacitive touch switch). The Mini Morse was able to replace the Ke:nx hardware/software as well as the TASH mouse emulator. The microswitch remained as the mouse select.

It became apparent that the cables required between John's wheelchair and the computer system would become a problem. First they required another person to connect them each time John wished to use his computer. Second there would be long term durability issues as these cables were connected and re-connected. It was John who came up with the unconventional solution to these problems. This solution was to use his Infrared Remote Control Pad System for his SEGA game system as the wireless link from his wheelchair to the computer and Mini Morse.

This would require adaptations to both the transmitter and receiver of the Infrared Remote Control Pad System. The transmitter would be mounted on the wheelchair, powered from the wheelchair through the Bloorview Battery Adapter, which was already powering the Wireless Switch Link and Stanley door transmitters. The direction control pad was tapped into and a connector provided to connect it to the wheelchair controller's four ECU 2 outputs. The Sega "Fire" control buttons B and C were also accessed by the third right-hand microswitch acting as mouse select) and the left-hand little finger capacitive touch switch (morse code character output).

The receiver normally obtained power from the SEGA Control Deck which would not be present when used with the computer. It was necessary to provide it with an external AC adaptor and DC voltage conversion circuitry. Connectors were added to the Sega receiver to take the "Fire B", "Fire C" and FWD direction control pad signal and convert them into three single switch outputs. These plugged directly into the Mini Morse.

John's Mini Morse meanwhile had been modified by Bloorview's software programmer to accept input from three switches. Input from switch I would be decoded as Morse code character input. A switch closure through switch input 2 would initiate a scanned mouse movement (7). Switch input 3 would act as mouse select button. This combination of Macintosh and Mini Morse, with capacitive touch switch, microswitch and sip and puff controlled ECU output, linked by the SEGA remote game pad, proved to be the optimal system for John.


John came to the clinic an experienced technology user with some fairly specific ideas on what he would like from a writing aid system and how he would like to access that system. He was an important and integral part of the assessment and prescription process providing insights into the wheelchair/ECU technology that he already used. His ideas for blending and customizing his new writing aid system, with other available commercial technology were invaluable. The system incorporated many parts of John's existing technology, integrating old and new into one overall system. John now has this system at home, providing him with independent access to a writing aid which will help him meet his future academic goals.


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3. Snell, E., Silver, L., Ridpath, C. The CHEC 2 Integrated Environmental Control System." In Proceedings of the RESNA 15th Annual Conference Toronto, Canada, June 17-22, 1994, pp.561-563.

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7.Ridpath, C., Snell, E., Silver, L., "MiniMorse Morse Code and Mini-keyboard Access to Popular Computers, Proceedings of the CSUN Conference, Los Angeles, California. March 1994.