Input keyboard with increased number of keys for an electronic device with a limited number of connecting pins

An input keyboard for an electronic device including a microprocessor having a limited number of connecting pins, of the type comprising:

• i) at least two primary conductive lines each connected to at least one primary connecting area and to one connecting terminal, each connecting terminal being adapted to be connected directly to a connecting pin of said microprocessor,
• ii) at least one first secondary conductive line, one second secondary conductive line and one third secondary conductive line each connected to at least one secondary connecting area and to one connecting terminal,
• iii) at least three input keys each adapted, when operated, to establish contact between a primary area of one of the primary lines and a secondary area of one of the secondary lines so that each of the primary and secondary lines is placed in a “high” state at its connecting terminal,
• which keyboard further comprises at least first processing means and second processing means each including at least:
• one first input connected to the connecting terminal of the first secondary line or the second secondary line, respectively,
• one second input connected to the connecting terminal of the third secondary line, and
• one output adapted to be placed either in the same state as the first secondary line or the second secondary line, respectively, to which it is connected if the third secondary line is not in its high state, or in the high state if the third secondary line is in its high state, each output being adapted to be connected to one of the connecting pins of the microprocessor so that it can determine each key operated as a function of the respective states of, firstly, the primary lines and, secondly, the outputs of the first processing means and the second processing means.