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The TS Files

TS File #..8

Environmental Control System:

Client: Male, late thirties. Has muscular dystrophy. Ventilator dependent.

Devices to be operated: Telephone, Computer,
Computer - power, Other mains appliances.

The main area of activity was a computer work station, with clear access for a wheelchair user. The most reliable method of operating switches was by jerking forward with the lower legs. Two switches were mounted with horizontal plastic spring bars approximately 400mm above floor level under the desk. The mounting had a degree of give, so no damage would be caused if the user 'docked' his wheelchair into position too fast. One switch was operated with each leg.

A switch selector unit with 2 switch inputs was designed. This unit had to support dual switch scanning, and use the same two switches for other controls. As the scanning use always required short switch closures, we used the selector switch to directly connect to the computer, and it only passed on a selection' signal if the switch was held in for more than a couple of seconds. While sounding clumsy, in practice this approach worked very well.