1. Start the Registry Editor (regedit.exe).
2. Locate
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{50906CB8-BA12
-11D1-BF5D-0000F805F530}.
3. Under this key locate the device instance, which represents your
RealPort device. As an example, if the device is the first instance the
location would be 0000\Parameters\1. If there are multiple devices
installed, simply review all of them and locate the key with the setting
PortName, with an assigned value of COMx (where x is the COM number of
the device you are looking for).
4. Add a new DWord key, of ForceRTSToggle. 
5. Set this key to a value of 1 (enabling RTS Toggle).
6. Either reboot the computer or disable and re-enable the RealPort
device from within the Device Manager.