At Command - Toshiba Satellite Pro L450 Series Manual

AT Command

-V90=*
-V90=0
-V90=1
User's Manual
V.90 Dial Line Rate
-V90 sets the maximum V.90 downstream that the
modem attempts to connect
V.90 disabled
V.90 enabled: automatic speed selection -
maximum modem speed(default)
C-3