(57) @ A membrane switch panel has a printed circuit base board (20) carrying bare copper
electrical circuitry (26) and contacts (26 & 28). A flexible, non-elastomer, laminar
membrane (22) overlays the board (20) and also carries a bare-copper contact (24).
An electrically insulating spacer (3) is provided between the board (20) and the membrane,
but it is provided with an opening to allow the contact (24) upon local depression
of the membrane to bridge the contacts (26 & 28) in the base board (20).
The membrane (22) is adhesively sealed to the base board (20) enclosing an atmosphere
of limited tarnishing ability for the contacts (20, 26 & 28) to maintain a low contact
resistance and allow non-precious metals to be used for contacts.
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