One of the most common tropes in fiction is which color wire to cut to defuse the bomb.
What’s the real situation?
Is there some kind of wire color coding convention?
Are these used in “legitimate” weaponry (police, FBI, military)
Are these universal (independent of region)
Do common criminals care? Do smart criminals care?
Are these conventions useful to the survival of the bomb builder?
Assuming a super smart criminal, who randomizes or unifies the wire colors, what other indicators besides wire color can the defuser use? What are some common trips?
I am not a bomb-disposal technician of any kind but it occurs to me that unifying the color of the wires while putting the device together would be a great way to commit explosive suicide.
“Was it the blue wire or the blue one?” BOOM! “Shit, I guess it was the blue one!”
Yeah. When building anything electrical, it’s pretty useful to know which bit is the positive, and which is the negative, unless you happen to *want *to cause a short. And I’m guessing a short circuit connected to a bomb is a Bad Thing (although I’m pretty sure the guys rig up the delaying mechanism and detonator first, *then *connect it to the explosive. I’m also going to guess messing with soldering irons next to explosives is a Bad Thing, too ).
However, as far as I know the colour coding is not universal - traditionally, it’s red positive, black (or blue) negative/ground, but I’ve also seen yellow/green, red/white, yellow/black… the important thing is the contrast, not the actual colours.
As for indicators the bomb defusal guys can use, well, reading the circuit itself is pretty easy, assuming it’s something common like rigging dynamite to an alarm clock, or even something a little bit more evolved, with a printed circuit and microchip timer/radio receiver. I suppose it could be possible to obfuscate things, say, by soldering dozens of fake wires, and/or multiplying the number of power sources and triggering devices, that way the bomb defusal guys doesn’t know which one is the correct one…
Then again, in real life bomb defusing guys rarely bother with “cutting the red wire” - they isolate the whole apparatus and blow it up on purpose in a safe disposal place, like an explosive locker or a patch of empty ground.
The “do I cut the red wire or the green wire” stuff makes for great drama, but it’s nonsense. There is no universal color code, especially for homemade bombs. There’s none of this cut the wire and the timer stops nonsense either.
If they are going to cut a wire, they look for the wire going to the detonator. If you cut the wire that makes it go boom, it doesn’t matter if the timer goes off or not. No power to the detonator means no boom. Period.
The problem is that bomb makers know that anyone trying to diffuse the bomb is going to cut the wire to the detonator, so they put in fake detonators with the real one underneath and use all sorts of tricks like tilt sensors so that if you cut the wrong wire or you manipulate the bomb too much it goes off. As Kobal2 said, this is why, if they have a choice, the bomb disposal guys will just isolate the bomb somewhere and blow it to bits.
Is cutting the wrong wire really going to make a bomb go off? You do not normally need electric current to stop something exploding do you? I can see that, in principle, you could have a booby trap wire (or several) holding an electromagnetic relay switch open or something, but would your average bomber really bother with such refinements?
ETA: Well, I guess if they actually bother to put in fake detonators in real life, maybe so. But is e-c-g talking about real bombers, or movie ones?
Red positive, black negative. Except for thermocouples, in which red is negative.
Chassis ground is green or bare. Hot is black, neutral white. Alternating current that is not biased with respect to ground is yellow and yellow. In three phase delta power, yellow, orange and brown. If it’s three phase Y, the center one is black.
Phone is red and green, or yellow and black for the second circuit, or blue and white for the third.
But it varies by region. Light blue means something special in Europe, but I don’t remember what.
Cables generally use black, brown, red, orange, yellow, green, blue, purple, gray, white for numbers 0 through 9. So in RS232 cables going to D-submin 9 pin connectors, the two most active lines are red and orange.
But, mad bombers don’t play by the rules anyway. That’s why they are mad bombers.
Can the guy holding the dikes afford to assume he’s dealing with a below average mad bomber ?
I suppose it depends on what scenario we’re talking about - I would WAG people who rig ten IEDs a day out of discarded arty shells to lay by the side of the road in Afghanistan don’t really bother with super advanced tricks, as those bombs are essentially just mines or booby traps : the point is to slow people down and harass them. If the device blows up in somebody’s face, that’s a bonus, but holding the grunts in place while they’re waiting for the bomb disposal team to show up works just as well. Keeping the enemy on his toes and paranoid is the real objective.
But if we’re talking mail bombs or spy-like sabotage, well… we’re back to “can you take the chance the guy’s an amateur ?”
If there’s sufficient time on the bomb’s timers, it won’t matter. The police can freeze the bomb, stopping it in its tracks and then find a way to dispose of it.
There was a recent episode of NCIS where Gibbs cut a wire (McGee suggested a different one) and the timer stopped and the bomb didn’t go off. Turned out the bomb makers had put in an anti-tamper circuit and it was the wrong wire, but the screwed up the explosive.
Real world bombs range from very crude to very sophisticated. Ted Kaczynski (aka the Unabomber) made some very sophisticated bombs, for example. He made his own switches and screws to make it harder to trace his bombs, and included anti-tampering devices in the bombs to make them harder to defuse.
A lot of the terrorists in Iraq are making more and more sophisticated bombs as well, to try to counter the U.S. bomb disposal units. It’s been a bit of an arms race over there between the terrorists and the bomb disposal guys. The terrorists started out with simple bombs, which the bomb disposal units could easily take care of. Then the terrorists started attaching cell phones to detonators, so when the bomb disposal guy came along they would call the phone and make the bomb blow up in his face. So the bomb disposal guys started jamming all cell phone frequencies. And so it goes, back and forth, with more and more sophisticated techniques and booby traps built into bombs and such.
The IRA in the 70s and 80s was also well known to make bombs that were specifically designed to blow up when tampered with or were attempted to be defused.
Since digital timers is a mature technology, the manufacturing of them has been culled to a handful of plants. Through an agreement signed by Member States of the United Nations, all timing chips have special embedded circuitry (similar to the money-copying prevention found in laser copiers) that creates a window of opportunity within the last 007 seconds of detonation. If an agent knows of this technology, he can safely cut any wire within the last seven seconds and the bomb will not go off. Due to he secretive nature of the technology (it would be self-defeating to let this go mainstream), the practice of hemming and hawing over which wire to cut evolved to cover the waiting out of the clock. (Note: this only works with bombs that have visible countdown clocks. Fortunately, in a separate but similar agreement with munitions manufacturers, it is virtually impossible to trigger a detonation without such a clock.)
One thing that I noticed many times in movies, we are shown the timer counting down, somebody cuts a wire (of course, it is the right one no matter which color he cuts) and the timer stops with only a few seconds left.
Now, if the power to the timer was cut, which would appear to be the case if it stopped, wouldn’t the timer go completely off instead of showing how may seconds are lefted.
If they are defusing a (say) government built bomb then presumably there are manuals the good guys have (or knowledge they have since they build the things) to say which is which. I presume anyway that a given builder holds to a set of rules of what color does what.
The best of this was in the Abyss when, due to using a green glow stick, the colors could not be discerned even though he knew which color to cut.
Oops, sorry. I thought linking to The Big Bus (a spoof) in the first one would have made the seriousness-level pretty clear. The 007 was a nod to Goldfinger. Here’s the belated smiley:
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