Their disadvantage is that they have to be scanned physically by a line-of-sight reading device.
They usually are operated by remote human pilots linked to the vehicles through line-of-sight datalinks or satellite downlinks.
Transmissions in the millimeter band are typically used in line-of-sight applications because they do not bend or reflect well.
The Linkbot itself has two rotating hubs with absolute encoding, along with an accelerometer, buzzer, multicolored LCD and ZigBee wireless system with a 100m line-of-sight range.
Now the larger version, a new class we dubbed the F-class, has been specially configured for being able to carry very large and over-dimensional pieces, and has no line-of-sight issues.
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In the air, planes will actually be nearer to the orbiting device, rather than farther away, and assuming a line-of-sight link from the road, the truck can work out kinks at a fraction of the cost.
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"This means that by watching what happens to the positions of the quasars on the sky as the gravitational field of Jupiter moves past their line-of-sight, the scientists can test other aspects of the general relativity theory, " says Professor Shanks.
The Lexington Institute's Loren Thompson says those mishaps usually result from a simple break in the line-of-sight connection between a plane and the satellite that controls it--often when one of the aircraft's own wings maneuvers into the path of the signal.
The TechStat Toolkit provides a comprehensive guide for organizations to establish their own TechStats to improve line-of-sight between project teams and senior executives, increase the precision of ongoing measurement of IT program health, and boost the quality and timing of interventions to keep projects on track.
It's palm-sized with a single blue LED light indicating a connection, but honestly you don't ever need to look at it: it doesn't need line-of-sight to your handset because it uses a wireless protocol called WiFi Display, which means you can happily leave it dangling out of the way behind your TV.
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By some strange reflex that I had previously never used, I picked up the line - my first and last sight of the ball, I might add - and opted to leave it well alone.
The galactic centre can only be observed at certain wavelengths - such as X-rays - because large amounts of dust lie in our line of sight, blocking out optical light.
The gadget does share a constraint common to all satellite-connected gear: Line of sight to the sky is required for connectivity.
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Having finally got sight of the Saracens try-line, Northampton seemed revitalised, and stayed camped in opposition territory for the remainder of the game.
If that was bad enough for the watching Johnson, the sight of Giteau motoring onto an overthrown line-out and into wide open spaces would hardly have brightened the England manager's mood.
The most you can expect by way of scene-setting here are occasional keen-eyed observations by Jesse Stone, the hero, of the women who cross his line of sight.
Fa'atau jinked his way to within sight of the line before passing to Evans, who showed great strength to stay in-field near the corner flag as he twisted in Mark Jones' tackle to touch down.
For the final group, he creates a focal point in a different part of the room "maybe a self-serve bar that's within sight line and they have access to the TV, but they can interact and talk, " he says.
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Infra-red communication suffers the same problems, but has the additional limitation of requiring a direct line of sight between objects as anyone who has tried to operate a television remote control with someone else standing between him and the television will know.
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