Patent ID: 8314352

Claim:
A two-level pressure sensitive keyboard, comprising: a base; at least one key to be depressed in response to a first pressure or a second pressure; and a membrane switch circuit module disposed over said base and under said key, wherein when said key is depressed to push said membrane switch circuit module, a lightly-depressed sensing signal or a heavily-depressed sensing signal is generated, wherein said membrane switch circuit module comprises: a first-layer membrane circuit board having a first contact corresponding to said key; a first spacing layer disposed under said first-layer membrane circuit board, and having a first perforation, wherein said first spacing layer has a first thickness; a second-layer membrane circuit board disposed under said first spacing layer, and having a second contact and a third contact, wherein said second contact is formed on a first surface of said second-layer membrane circuit board, and said third contact is formed on a second surface of said second-layer membrane circuit board and electrically connected with said second contact, wherein when said key is depressed in response to said first pressure, said second contact is inserted into said first perforation to be contacted with said first contact, so that said lightly-depressed sensing signal is generated; a second spacing layer disposed under said second-layer membrane circuit board, and having a second perforation, wherein said second spacing layer has a second thickness; and a third-layer membrane circuit board disposed under said second spacing layer, and having a fourth contact, wherein when said key is depressed in response to said second pressure, said fourth contact is inserted into said second perforation to be contacted with said third contact, so that said heavily-depressed sensing signal is generated, wherein said first thickness and said second thickness are different, wherein said first-layer membrane circuit board comprises plural scan input lines, said first contact is connected with a first scan input line of said plural scan input lines, said second-layer membrane circuit board comprises plural scan output lines, and said second contact and said third contact are connected with a first scan output line of said plural scan output lines, wherein said plural scan output lines and said plural scan input lines crisscross to define a first-layer keyboard scanning matrix corresponding to said plural keys.