WF AUTOMACAO wrote:

>> I am looking for something with 3 or 4 channels (from the system's
>> side) that also carries a filter.

  Not *this* needs further explanation.  Extra wires (if I gather this
correctly) is a pretty expensive way to implement CSMA/ CD.

>> 5. Is there an IC or a circuit that i can use to interface a 4x4
>> matrix keyboard?
> 74922

  74C922 actually.  Or a PIC if cheaper and more available.
--
  Cheers,
        Paul B.