91 lines
4.9 KiB
Plaintext
91 lines
4.9 KiB
Plaintext
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**Chrome Box Plans**
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Emergency vehicles in many cities are now using devices called OptoComs.
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OptoComs are a system of sensors on traffic lights that detect a pattern of
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flashes from vehicle-mounted strobe lights. This flash pattern varies from
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city to city depending on the manufacturer of the equipment used. Often the
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sensors are installed only at major intersections. Nevertheless, the Chrome
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Box, which simulates these strobe patterns can often be used to give your
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car the same priority as an ambulance, paramedic van, firetruck or police
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car. Because of the varying patterns on different systems this phile will
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outline a general procedure for making the Chrome Box.
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Decoding Flash Patterns:
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First, you need to observe an emergency vehicle in action. You can wait
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until you encounter one by chance, running out to see when you hear a siren,
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or when you pull over in your car to let one pass by. You might wait near a
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fire station for the next emergency to occur. Or, if you are very impatient,
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you can summon one by calling in a false alarm (not recommended in areas
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with limited services that could divert attention from a real emergency).
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If the OptoComs in your area are the kind with a pattern of single flashes
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at a steady rhythm, you have merely to buy a strobe light at Radio Shack &
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adjust the flash rate until you can induce a traffic light to change.
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If the flash pattern is more complex, you can videotape the emergency
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vehicle & then play back the tape in single-frame mode, counting the number
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of frames between each flash. Each video frame is 1/30 of a second, using
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this you can calculate the time between flashes in the pattern. Another way
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is to count the number of flashes (or flash-groups) in one minute and use
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that to compute the rate. Counting video frames will give you a good idea of
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the spacing of the flashes in a complex pattern. For really accurate
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information, call the fire station & ask them, or write to the manufacturer
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for a service manual, which will include a schematic diagram that you can
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use to build one. A good cover story for this is that you are a consultant
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& one of your clients asked you to evaluate Optocom systems, or you could
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pose as a free-lance journalist writing an article.
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Modifying the Strobe Light:
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You may not have to modify the strobe at all. But if you need a faster
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flash rate than your strobe allows, open it up & find the large capacitor
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inside. Capacitors are marked in microfarads, abbreviated as mf,mfd or ufd.
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By replacing the capacitor with one of the same voltage-rating (usually 250
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volts or more) and a SMALLER value in microfarads, you can increase the
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flash rate. Halving the microfarads doubles the rate.
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The other component that can be changed is the potentiometer (the speed
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control device with the knob on it). Using a smaller value (measured in ohms
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or Kilohms, abbrevaited with the greek letter 'omega' or the letter K) will
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speed up the strobe. There may also be a resistor (small cylinder with
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several colored stripes on it, and wires coming out of each end). Replacing
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this resistor with one of smaller value will also speed up the strobe.
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To generate a complex pattern, you will either have to design and build a
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triggering circuit using IC chips, or rig up a mechanical device with a
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multiple-contact rotary switch and a motor. It HAS been done.
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To modify the strobe for mobile operation the simplest thing is to get a
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110-volt inverter that will run off of a car battery by plugging into the
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cigarette lighter & run the strobe from that. Or, you can figure out
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(or find in a hobby electronics magazine) a strobe circuit that will run
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from batteries. Battery-powered strobes may also be availble, either
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assembled or as kits.
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Stealth Technology:
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Most light sensors and photocells are more sensitive in the infrared area
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of the light spectrum. Infrared (IR) is invisible to the human eye. Putting
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an infrared filter over the strobe light may allow the Chrome Box to
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operate in traffic undetected by police or other observers. IR filters can
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be obtained from military surplus sniperscope illuminators, or from optical
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supply houses like Dow-Corning or Edmunds Scientific Co.
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Using the Chrome Box:
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Mounted on your car, the Chrome Box can guarantee you green lights at major
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intersections in cities that have OptoComs. Handheld Chrome Boxes may be
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used to create gridlock by interfering with the normal flow of traffic.
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If you have access to a window overlooking a traffic light, you can play
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pranks by switching the signals at inappropriate moments, or you can plug
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the strobe into an exposed out let at a laundromat or gas station.
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Soe Decoded Patterns:
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Torance, California
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Standard large Radio Shack strobe lights are used. Moderately fast rate.
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* * * * * * * *
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Manhattan Beach,CA
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Flash-pairs in a 4:1 ratio, at a rate of 2 flash-pairs per second.
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* * * * * * * *
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<------ 1 sec ----->
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