PCMCIA modem & lost characters

[brendan@clark.net (Brendan Hoar)]

On a thinkpad 360Cs I have installed an "IBM High Speed PCMCIA Data/Fax
Modem" model FC3635.

What sort of serial interface does it have or mimic?  I consistantly get
lost characters at 19200 under Windows v3.1 using different comm programs.

Anyway to activate some sort of buffering?  An old DOS utility says that it
does not have a 16550 compatible interface.

Thanks,
Brendan