Patent ID: 7224344

Claim:
An apparatus for filtering out selected key codes transmitted between a keyboard and a host computer, the apparatus comprising: an input port configured to receive a stream of key codes transmitted from a keyboard, wherein key codes of the stream of key codes comprise make key codes corresponding to keys that are pressed, and release key codes corresponding to keys that are released, and wherein each key on the keyboard is characterized by a unique make key code and a unique release key code; a filtering module, operably connected with the input port and storing a rules table containing key codes, combinations of key codes, and rules associated with each key code and the combinations of key codes, each rule specifying whether a key code and combination of key codes is to be blocked or transmitted, a make list storing a list of make key codes that have been received and transmitted to the host computer and for which corresponding release key codes have not been received, and a block list storing a list of make key codes that have been received and blocked from the host computer and for which corresponding release key codes have not been received, wherein the filtering module identifies combinations of key codes as the key codes of the make list, the filtering module configured to block only key codes and combinations of key codes of the stream of key codes selected in accordance with the rules table; and an output port, operably connected with the filtering module, the output port configured to pass unblocked key codes to a host computer, wherein the combination of key codes corresponds to a combination of keys being pressed simultaneously.