

UK police are putting tactic to use to fight crime


I. Industry's Silent Song




Power Grid grid
[Image Source: UCSC Silicon Valley Extension]





London gang suspects
London Gang guns
[Image Souce: PA]




Source: BBC

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youre all missing the mechanism
By yoduh on 12/18/2012 4:57:23 AM , Rating: 2
ok, thats somewhat overstated, but..

The signal being recorded, then used to verify a recording
is the jitter on the 50hz signal - there is no "drift" - the carrier frequency doesnt change, to theres no time-of-day error accumulating.

More importantly, when judging whats detectable, you should consider whether you can hear a flat clarinet in the reed section - my bet is that an audiophile could. More to the point, you could tell when a quarter note was spliced out of the middle of "sympathy for the devil"

As regards the supposed immunity of the phone system to hum, you seem to forget that there are harmonics, which would clearly survive the filters cuz theyre in the audible range.

In principle, the power company can tell what kind of appliances youre using, and when you turn them on - incandescent bulbs have a very different startup power-draw profile than florescent bulbs, SCRs used in dimmers actually cause power delivery problems for power companies, too many of them and volts-and-amps get out of phase, reducing power delivered. Theres potential that police can use this to identify pot-growing operations. Now this kind of thing must be done near the house, not at the power station, but with the advent of smart-meters, this is trivially doable with the on-board MCU and some good code (downloaded thru the mains!)

Id acknowledge that not all "forensics" is equal - bite mark matching is basically rubbish - and prosecutors have their favorite "expert" witnesses, but dismissing the technique is simplistic - "I cant do it, so it must be impossible" is shortsighted.

