ShadowKnows
July 16th, 2007, 02:22 AM
I just learned about a fusing system called a cascading optical trigger. Apparently, one of the reasons the Boston cops got so freaked out by those Lite-Brite pictures is that the Lite-Brite resembles a cascading optical trigger, an electronic fusing system that is reputedly almost impossible to defuse.
Information on COTs is nearly impossible to find online, but I was able to find a written description which I'll post here for the benefit of forum members.
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A Cascading Optical Trigger is a fusing device that uses optical photocells in series/parallel. As you probably know, an optical photocell is both a resistor and a capacitor. The signal path is dependent upon which cells are simple used a capacitors, and which are used a actual flashes.
In this way, the signal can be transmitted in more than one path, some by simple electrical path, some by one flash triggering another, and in some bases both. So, the result is that it is extremely difficult to figure out the signal path.
Pulling a photocell out of the sequence could reduce the overall capacitance and permit the electrical signal to run unfettered to the final trigger point. Pull the right one, and you defuse. The problem is that with, for instance a dozen, the permutations reach the millions. So, you'd have a one in several million chance of pulling the right cell out of the series.
If you had the wiring diagram, it would be a slamdunk. But, most bomb planters don't leave their wiring diagrams with the device! Now, that would be a bad EOD expert.
This concept was originally developed for small nukes. (Dambusters, bridge burners, etc.) Then, even if they were detected before they detonated, the probability of being defused approaches zero.
--
If you have any more information on COTs, feel free to post it in this thread.
Information on COTs is nearly impossible to find online, but I was able to find a written description which I'll post here for the benefit of forum members.
--
A Cascading Optical Trigger is a fusing device that uses optical photocells in series/parallel. As you probably know, an optical photocell is both a resistor and a capacitor. The signal path is dependent upon which cells are simple used a capacitors, and which are used a actual flashes.
In this way, the signal can be transmitted in more than one path, some by simple electrical path, some by one flash triggering another, and in some bases both. So, the result is that it is extremely difficult to figure out the signal path.
Pulling a photocell out of the sequence could reduce the overall capacitance and permit the electrical signal to run unfettered to the final trigger point. Pull the right one, and you defuse. The problem is that with, for instance a dozen, the permutations reach the millions. So, you'd have a one in several million chance of pulling the right cell out of the series.
If you had the wiring diagram, it would be a slamdunk. But, most bomb planters don't leave their wiring diagrams with the device! Now, that would be a bad EOD expert.
This concept was originally developed for small nukes. (Dambusters, bridge burners, etc.) Then, even if they were detected before they detonated, the probability of being defused approaches zero.
--
If you have any more information on COTs, feel free to post it in this thread.