The term Telemetry, originates from the Greek words, tele meaning remote, and metron meaning measure. The modern dictionary states that it is the science and technology of automatic measurement and relaying of data by wire, radio, or other means from remote sources, as from space vehicles, to receiving stations or system designers or operators for recording and analysis. The primary purpose of any telemetry system is to gather data at a place that is remote or inconvenient, and to report the data back to a "point of contact" where the information is evaluated. Telemetry refers to wireless communications, and is used generally in testing of moving vehicles such as cars, aircrafts, missiles and satellites. National Aeronautics and Space Administration (NASA), European Space Agency (ESA) and other space agencies employ telecommand systems to gather data from orbiting spacecraft and satellites. Telemetry is also used in applications such as electric and water meter reading. This has proven to be more cost effective than having a "meter reader" come by to read your utility meter.

This term also relates to data transfer over other mediums, such as telephones or computer networks. When this system is used for both control and data collection, the term supervisory control and data acquisition is applied. Telemeter is the apparatus used for recording the readings of an instrument and transmitting them by radio. After each telemetry record is read into core, selected data items are extracted and placed into arrays for subsequent processing. Sometimes this process requires extracting and examining the values of one or more data items before the extraction of other items. For instance, a flag in the data indicates which of several formats the data appears in, and the location of other data items within the record depends on this format.

Biomedical telemetry or biotelemetry is the monitoring of biological information from animals and man. The importance of this to basic biological, environmental and medical research cannot be overstated. Since the early 70s, the technology to provide real time physiological monitoring in the medical care units became widely recognized. This technology is used for long-term monitoring of the electrophysiological state of patients who are at risk of abnormal heart activity. In a CCU (coronary care unit) such patients are typically equipped with automatic recording, measuring, and transmitting devices. An alerting function immediately summons nurses if the patient is suffering from a critical condition. I myself have used this type of device when in the hospital for what appeared to be a heart attack (lucky it wasn't).