A speech recognition (SR) dictionary switching unit selects a SR
dictionary including commands that are for controlling target devices and
selectable in current operating states detected by a device-state
detecting unit. When a SR engine recognizes an uttered command of a user,
it collates the speech with the commands included in the selected SR
dictionary. If the command is not selectable in the current operating
states of the target devices and is one of a reciprocal pair of commands
working oppositely to each other, the other of the reciprocal pair is
substituted for the command. This results in decreasing unreasonable and
unpleasant feeling of the user in voice manipulation.