Zero Force Switch - ideal aid to physically challenged


The zero force switch came about as an answer to a problem. The problem was that I was approached by a researcher at the Calgary childrens hospital while working at a local electronics supply store about finding a suitable device for a child suffering from extreme strength limits preventing the child from operating anything that required pressure. The child could not operate the buttons on a phone or call buttons so could not call for help and as such required round the clock presence of a caregiver.

At the time there was no such device found amongst the 17000 suppliers at our disposal.
Using capacitive technology a touch plate keypad system was possible using components locally stocked which could be designed with pads large enough for the child access and which would require less than .1 grams of pressure to
activate.
The first hurtle was to design such a keypad. The second hurtle was to comply with the phone company's Terminal-connection-program rules.
Depicted above is the touch pad keypad which could wire into the keypad of a standard push- button telephone. Unfortunately, the local telephone company would not allow such a device to be a replacement for the standard keypad unless manufactured by a registered telecom device manufacturer.

My design was therefore just turned over to the researcher to find a phone manufacturer to take it on, or to modify the design to trigger a different call method.