Ghostscript parameters to convert PDF to fax TIFF with no dithering

I need the best parameters to use with Ghostscript (from version 8.70) on CentOS to convert a generic multipage PDF to a multipage fax tiff file. I have the following parameters working, but the dithering makes the fax ugly. I need to apply a threshold, so anything below (for example) 50/100 grey is white and the other is black. I repeat, no dithering. The current gs options used are: -r204x196 -dBATCH -dPDFFitPage -dNOPAUSE -sDEVICE=tiffg4 I don't want to use ImageMagick, this job needs to be done with a single pass in ghostscript. In attach you'll find the original file, [login to view URL], the bad currently produced file, [login to view URL] and how I want the file to be produced by ghostscript, good.tif. The payment will be made only when the parameters will be verified by me.