Patent US 5,774,858

A speech analysis method of protecting a vehicle from unauthorized accessing and controlling has a mode of voice changing and a mode of changing a protection degree. In the voice changing mode, a system realizing the method is interactively entered in advance a voice password, voice service passwords including a voice changing mode service password, and control commands. The passwords and commands are analyzed in a voice dependent and voice independent modes and stored. Then, the voice changing mode service password is entered into the system the system, is taught the passwords and commands in the voice changing mode and transferred in an operational state. In the mode of changing protection degree, after the passwords and commands, including a voice service password for changing a system protection degree, are interactively entered into the system in advance, the protection degree is changed through interactively entering the protection degree service password the system is taught the password and the commands at the changed protection degree and transferred into the operational state.