The rapid introduction of electronic switching systems with Stored Program Control (SPC) has made possible the interconnection of the control processors by high-speed data links to provide common-channel interoffice signaling (CCIS). Not only does this permit higher-speed, lower-cost, more reliable setup of connections, but also the transfer of packets of information for more flexible call control. The papers in this issue describe the evolution of the SPC network concept since the introduction of CCIS in 1976 and the first new services which will exploit the power of this new network capability.