Abstract: A method and apparatus used in the context of a first and a second communications network, wherein the second communications network is overlaid upon the first communications network. The invention generates and utilizes a number of flags and indicators to determine which channel, from among a plurality of shared channels assignable to a first communications network (e.g., an AMPS network) and a second communications network (e.g., a CDPD network), will be used next for communicating information by the second network (e.g., a CDPD information). The invention provides a means for generating an ordered Idle.sub.-- Channel list. The Idle.sub.-- Channel list includes each assignable channel that is not currently used by the first or second communications network. In one embodiment of the present invention, the order of the channels in the Idle.sub.-- Channel list at any given time determines the order of the channels to be selected for transmission of a signal by the second communications network.