Transmitting communications signals represents one of the the earliest and most popular uses for satellites. Early examples such as Echo were passive devices, large metal-coated inflatable balloons off of which radio signals were bounced from one location on the Earth to another. Another interesting passive example was the United States' project West Ford launched in 1963. This consisted of a cluster of metal needles acting as dipole antennae, reflecting signals from the Earth. Today's communications satellites are far more sophisticated.
Broadcast satellites relay television programming directly to home subscribers.
The new Iridium satellites will expand the range and capabilities of mobile telephony. A reassuring network of Search and Rescue satellites listens for transmissions from the Emergency Position Indicating Radio Beacons used by boaters, Emergency Locator Transmitters used in aircraft, and Personal Locator Beacons used by individuals in remote areas. There are even satellites devoted to amateur radio transmission. Much discussion has centered around the placing of military weapons in orbit. However, the vast majority of military satellites in orbit are used for communications or surveillance purposes.