The Communications Security Establishment (CSE) is Canada's national Signals Intelligence (SIGINT) organization. SIGINT, as defined by the Canadian government, is "all processes involved in, and information and technical material derived from, the interception and study of foreign communications and non-communications electromagnetic emissions." Subcategories include intelligence derived from communications, also known as Communications Intelligence (COMINT), intelligence derived from non-communications emissions such as radar, also known as Electronics Intelligence (ELINT), and intelligence derived from the telemetry transmissions of missiles or other equipment undergoing testing, also known as Telemetry Intelligence (TELINT). Note that SIGINT is restricted to foreign emissions under the Canadian government definition.
Strictly speaking, CSE is only part of Canada's SIGINT effort. A civilian agency of the Department of National Defence, CSE processes SIGINT, produces analyses, and disseminates reports to Canadian and allied consumer agencies. The actual collection of the SIGINT, however, is conducted by the Canadian Forces Supplementary Radio System (SRS), a component of the Canadian Armed Forces that operates under the direction of CSE.
CSE and the SRS in turn work in close co-operation with the giant American and British SIGINT agencies, the National Security Agency (NSA) and Government Communications Headquarters (GCHQ), Australia's Defence Signals Directorate (DSD), New Zealand's Government Communications Security Bureau (GCSB), and a number of other SIGINT agencies in a global intelligence alliance known informally as the UKUSA community. CSE maintains permanent liaison officers at NSA HQ at Fort Meade, Maryland (CANSLO/W) and GCHQ in Cheltenham, UK (CANSLO/L). There are also NSA and GCHQ liaison officers at CSE HQ (SUSLO/O and BRLO, respectively).