In an apparatus for improving voice clarity by controlling a gain of a voice based on a sound pressure level of the voice and a sound pressure level of noise, it is determined whether a sound pressure level of a gain-controlled voice exceeds a maximum allowable level. In accordance with one embodiment of the invention, a method is provided for user authentication, the method including receiving a usernamepassword pair associated with a user; requesting one or more responses to a first Reverse Turing Test ; and granting access to the user if a valid response to the first RTT is received and the usernamepassword pair is valid. The target floor registration units are connected to an elevator controller via an interface.