In light of Jon's comments and others, I am proposing a laser based system
that eliminates wires. The idea is that a laser shoots a beam across the
course to turning-optics that send the SAME beam to a photo detector (PD)
one mile away. When the car breaks the beam, that pulse hits the PD a mile
away and starts the requisite clocks. The "time of flight" for light to go 1
mile is approximately 0.0000053 second. That is FASTER (maybe 10%-15%) than
the electrons in a 1 mile long wire. Curvature-of-the-earth is a non-issue
because we are only dealing with 1 mile segments. The system is duplicated
at each mile. The penta prisms shown below can cost as little as $59-$300. I
mention this because it "might" be possible to assemble a reasonable
(affordable) system.
CW diode laser: Provides the beam that the car breaks. That "breaking-pulse"
is transmitted (at the speed of light) to the photo detector at the next
mile station.
http://lasercomponents.com/us/792.html?
<http://lasercomponents.com/us/792.html?&tx_bgmprodbfrontendlc_pi1%5brid%5d=
2128&cHash=c051ebbd96&MP=715-446>
&tx_bgmprodbfrontendlc_pi1[rid]=2128&cHash=c051ebbd96&MP=715-446
Here is another Laser. At 5 watts it is higher power.
http://www.laserdiode.com/products.cfm?product=14
Amplified photo detectors are used as clock triggers (500 picoseconds rise
and fall times).
http://www.psplc.com/product.asp?ProdID=detAmplified
Right Angle Bending Prisms. (beam turning mirrors) used to transmit the beam
pulse.
http://www.lambda.cc/PAGE124.htm
Penta Prisms (used for beam steering and to compensate for minor
misalignment)
http://www.lambda.cc/PAGE130.htm
See my DISCLAIMER in next post.
-Elon
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