ATX Form Card

Does anybody have any ideas on the circuitry on a ATX form card that was
used by a number of mobo companies to add PS/2 USB and IR to some AT boards.
They were attached to a blanking plate, and had a 20 pin ribbon cable on
that attached to the mobo. I have been able to find the pin outs of the
ribbon cable, bu the board had a number of capasitors and resistors between
the ping and the sockets.
The main port I want to get working is the PS/2 port so I can hook up a KVM
switch. Many thanks to anybody who can help

James Cronin