Telemetry measurements are made and other data collected at remote or inaccessible points and transmitted to receiving equipment for monitoring, display, and recording.
Originally, the information was sent over wires, but modern telemetry more commonly uses radio transmission.
Basically, the process is the same in either case. Among the major applications are monitoring electric-power plants, gathering meteorological data, and monitoring manned and unmanned space flights.
Aerospace telemetry for rockets and satellites was inaugurated with the Soviet satellite Sputnik, launched in 1957, and systems have grown in size and complexity since then.
Observatory satellites have performed as many as 50 different experiments and observations, with all data telemetered back to a ground station.
The techniques developed in aerospace have been successfully applied to many industrial operations, including the transmission of data from inside internal-combustion engines during tests, from steam turbines in operation, and from conveyor belts inside mass-production ovens.