Interconnection of an entrant's network involves two distinct steps. First the networks must be tied together by one or more links; then the links are used to convey traffic that originates in one network, passes through the other network (and possibly through segments of both), until it terminates on one or the other network. In the "classic" case of a purely long distance entrant, of course, all calls inevitably both originate and terminate on the incumbent PTO's network, but some calls are transmitted part of the way on the entrant's trunk lines. In every type of interconnection (with the sole exception of simple CPE), an additional network is linked to the pre-existing PSTN, so creating an extended switched network through which an increased volume of traffic can and normally does flow.