Abstract: The distribution of calls to directory inquiry centers is concentrated in a server which reduces the traffic between the centers. For a given center, the server cyclically determines a forecast waiting time of the calls as a function of an average waiting time per call which it estimates for the given center, and compares the forecast waiting time with two thresholds so as to decide to route the calls to the given center or to another, less heavily loaded, inquiry center, and with two other thresholds so that the given center accepts calls from other, more heavily loaded centers, or refuses them if it is itself saturated.