Abstract: The system has a speech recogniser (2) for recognising speech from a user and a synthesiser (6) for replying to him and engages in a dialogue with the object of enabling the user to convey to the system a piece of information such as a telephone number. The system builds up the number in a buffer (10). Each time it receives a string of digits, it reads it back for confirmation. When a number (or part of one) is read back, it is divided into “chunks” according to certain criteria: the positions of these divisions can be recorded to be taken into account in later processing. Responses are compared with the current buffer contents to determine whether they it should be interpreted as a correction, partial correction or pure continuation of the existing contents. Positions in the buffer at which pure continuations are entered are marked, to allow a “final repair” process in which, if the final result fails to match some criterion of acceptability (e.g.