I do not have a Card Properties page in Device Manager
Device Manager is accessed by opening the Control Panel, System, Hardware and then the Device Manager button. Depending on your operating system version and what product you have, there will typically be an entry for your serial card under Multifunction Adapters or Multi-port Serial Adapters. Any settings that are selectable for the card i.e. Duplex Mode, can be changed by double clicking on the card's entry and then selecting the Card Properties tab.
If your Card properties tab is not there please try the following, which is applicable to 2000/XP only:
1. Go to Start and press Run. Type regedt32 to open the registry editor
2. Go to the following folder HKEY_LOCAL_MACHINE\SYSTEM\CURRENT CONTROLSET\ENUM\PCI (or PCMCIA if applicable)
3. For PCI cards look for an entry with "VEN_135A" and right click it
4. Select 'Permissions'
5. Check the Full Control box to allow permission
6. Close the registry editor
7. Reboot the machine
8. Open Device Manager and the Card Properties tab is now be visible