An interconnect communication system is provided that provides for dispatch-type services including Instant Access call set up, talkgroup creation and management, and in-band floor arbitration and mode switching that employ in-band signaling tones. By providing talkgroup creation and management and in-band floor arbitration that are transparent to the underlying network, the talkgroup creation and management and in-band floor arbitration may be implemented in a legacy system without the need to modify the network and regardless of the type of network employed. Furthermore, by providing Instant Access call set up procedures and mode switching procedures that are capable of utilizing modified versions of known messages, the procedures may be implemented in a legacy system in a simplified manner, minimizing the impact of an addition of such procedures to a legacy network.