Debian installer, hardware speech synthesis

[John G. Heim]

I cannot figure out how to get the debian lenny installer to use my 
doubletalk LT. The installer manual says, "Support for hardware speech 
synthesis devices is available only alongside support for graphical 
installer. You thus need to select the "Graphical install" entry in the boot 
menu. Hardware speech synthesis devices cannot be automatically detected. 
You thus need to append the speakup.synth=driver boot parameter to tell 
speakup which driver it should use. driver should be replaced by the driver 
code for your device (see driver code list). The textual version of the 
installer will then be automatically selected, and support for the speech 
synthesis device will be automatically installed on the target system. "

But it doesn't actually say how to do that.  The other sections like the one 
about starting a serial braille display give some hints. It seems like I 
have to press tab, then type "speakup.synth=ltlk", and then press enter. But 
it doesn't work.