 General Dynamics C4 Systems, in Scottsdale, AZ, makes SIGINT products including the Army's Prophet ground SIGINT system.GTE Government Systems is now part of General Dynamics.GTE merged its communications operations with Verizon

A British firm that makes the "HARVESTER family of SIGINT database applications (that) provide unique and cost-effective solutions to a wide range of collection requirements" has a website that can serve as a basic tutorial on the technical aspects of what SIGINT systems collect.