1. A virtual network call processing system, comprising: a communication line interface configured to be connected to a source terminal and receive a calling message from the source terminal directed to an intended recipient; a call processor with a call pullback mechanism including, a data processor, and a computer readable memory having computer readable instructions encoded therein that when executed by said data processor implement a central office switch characterization mechanism that characterizes signaling attributes of signals produced by one of a plurality of central office switches that service different geographical locations, said plurality of central office switches each having a different frequency and cadence signal event characteristic; and a signal determination mechanism configured to determine whether the signals produced by said one of said plurality central office switches includes at least one of a fast busy signal, slow busy signal, ringing signal, answered signal, and ring-no-answer signal, wherein said signal determination mechanism is not informed of the frequency or cadence of the signals before said signal event occurs.