Since 2011, we have developed and deployed a standalone Voice-Interactive Digital Signage System to provide useful university information to users at the Nagoya Institute of Technology. This system comprises MMDAgent, a software toolkit to realize voice interaction with 3-D character named "Mei". An important shortcoming is that this system's ability is limited because it lacks a network communication function. This research newly presents a network communication function among several digital signage systems. This function enables collaboration of multiple signage systems through information sharing and other means.