Fred Rooks wrote me (Jan 2009):

Here's how I use your software in Dosbox through a USB2serial adapter:

USB-to-serial adapter

   1. Connect your USB-to-serial adapter to your projector and
computer. I am using one that is provided by STLab.
   2. Type ` dmesg ' and study the output. There should be five lines
which look roughly like this:
          [123104.024046] usb 2-6: new full speed USB device using
ohci_hcd and address 6
          [123104.237411] usb 2-6: configuration #1 chosen from 1 choice
          [123104.239231] pl2303 2-6:1.0: pl2303 converter detected
          [123104.272405] usb 2-6: pl2303 converter now attached to *ttyUSB0*
   3. Remember the device to which your adapter was assigned (in this
case ` ttyUSB0 ').
   4. Replace the first serial port device with a soft link to the USB
device to which your USB-to-serial adapter has been assigned:
          ` rm /dev/ttyS0 && ln -s /dev/ttyUSB0 /dev/ttyS0 '.

Since the /dev/ folder is populated each time you boot Linux, you need
to repeat this command again and again. More advanced users may devise
a script to manage the devices automatically.


Dosbox

To configure Dosbox so that it communicates with the serial port
device you need to edit your ~/.dosboxrc file. Just find the line that
reads:

` serial1=dummy '

and change it to

` serial1=directserial realport:ttyS0 '.

Now you can launch Dosbox and run the projector software.

   1. Open your terminal and cd to the Diashow folder'.
   2. Launch dosbox by typing ` dosbox '.
   3. When in the emulated dos environemnt, mount the current folder
as drive c and change to it:
           ` mount c: ./ '
           ` c: '
   4. Now type ` diashow ' to launch the projector software.


If everything is set properly and working, you should be able to
control your Rollei projector without the need for a proprietary
operating system.

Cheers,

Fred Rooks


Addition by Erhard Bollmann, 2015-09-20:
 An additional "chmod 666 /dev/ttyS0" is necessary