Robots can be operated from a distance by human beings. Computers can also be controlled from places far removed from the machines themselves. This is done by means of remote control.

A simple example of a remote-control system is the control box for a television (TV) set. Another example is a transmitter used to fly a model airplane. The TV control employs infrared (IR) radiation to carry the data. The model airplane gets its commands via radio signals. In this sense, both the TV set and the model airplane are robots.

Remote control can be done by wire, cable, or optical fiber links.Undersea robots have been operated in this way. A person sits at a terminal in the comfort of a boat or submarine bubble and operates the robot, watching a screen that shows what the robot “sees.”This is a crude form of telepresence. The range of remote control is limited when wires or optical fibers are used. It is impractical to have a cable longer than a few kilometers. A special problem exists for long-distance undersea remote control. Radio waves at conventional radio frequencies cannot penetrate the oceans, but extremely long cables present mechanical problems.

When the control station and the robot are very far away from each other, even radio, IR, or visible-light signals take a long time to cover the distance. A remotely controlled robot on the moon is about 1.3 lightseconds away. It is 2.6 s from the time a command is sent to a robot on the moon until the operator sees the results of the command.

One of the most dramatic examples of radio remote control is the trasmission of commands to space probes as they fly through the solar system. In these cases, the separation distance is of the order of millions of kilometers. As the probe Voyager passed Neptune, and a command was sent to the probe, the results were not observed for hours. Remote control of this type is a special challenge.

There is an absolute limit to the practical distance that can exist between a remotely controlled robot and its operator. There is (as yet) no known way to transmit data faster than the speed of electromagnetic (EM) energy in free space.

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