Abstract: The invention is a novel method of processing incoming and outgoing call requests by a switching unit such as a KSU, PBX or PC server. Each established circuit and each call request is associated with a priority. For an outgoing call request, if an available external bandwidth channel of the appropriate type is found, then a circuit is established at once. However, if there is no available external bandwidth channel of the appropriate type, then the priority of the outgoing call request is checked against the priority of the established circuits. If a lower-priority circuit is found, then that circuit is torn down and a new circuit is established between the internal bandwidth channel carrying the outgoing call request and the external bandwidth channel formerly occupying the established circuit that was torn down. In the case of an incoming call request, a destination terminal device and associated internal bandwidth channels will be specified and availability thereof is verified.