This paper presents a linguistic analysis of traintimetable requests uttered twice by users of a public telephone information service: they first formulate their request to a human operator, and then repeat the same request to what they believe to be a machine (in fact, the same operator using a vocoder). The purpose is to study the influence of the introduction of the machine on the users linguistic behaviour and therefore to observe to what extent these unconsciously controlled utterances may be processed automatically. We evaluated this influence with a parser (ALORS) particularly designed for accepting unconstrained and dislocated production, as it frequently occurs in speech.