insert the legend and the resistive membrane switch keypad

In some applications it is desirable to have the ability to customize some of the legends, either when the switch is assembled to the end product or in the field. This allows a customer to use one standard membrane switch for many different models of similar instruments. It also allows customizing a membrane keypad for specific applications.
Switches keypad can also be designed with legend cards that can be changed by the end user. One very successful application is a scoreboard with an insertable legend card for each sport. This allows the user to re-legend the switch for the sport that is being played. Consequently, the switch can be kept relatively small with only a few keys.
To design a switch with insertable legends, a clear window is put into the area that will have insertable legends. An oversized pocket is put behind this clear area so that the legend card can be inserted and seen through the window. The entire graphic overlay has the same texture, which helps hide the fact that legends are being viewed through a window. The diffusing properties of the texture are not a problem for viewing the legends because the legend cards are held directly against the overlay by the pocket.
It is also recommended that the background color be different than the color surrounding the window. This will also help disguise the legend card. The fact that a membrane keyboard has insertable legends can be almost completely transparent to the user if implemented correctly.
Thick Film Resistors
Screen printed carbon thick film resistors can be incorporated into a membrane switch flex circuit. The tolerances of the resistors determine their cost. Tolerances of +/- 10% can be held if required. In most cases these are relatively expensive resistors.

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