Multiport serialcard

[M. M. J. Weerasinghe]

Dear friends, I am using a multiport serial card for my Linux server and made available  for users to log in. However connection speed is very slow than conneting to it's own serial ports (ttyS0 & ttyS1). How can I set connection speed of ports at multiport card using "Setserisl". Every help is wellcome. Thanks in advance Jagath weerasinghe Airport & Aviation Services Ltd., Sri lanka