Earlier anti-theft money packs exploded in the robber's hand at the counter, so two Atlanta inventors made theirs wait until he'd already walked out

问题

Marked-money devices designed to foil bank robbers went off while hostages were still nearby

背景

换别人会怎么做

The available prior art had already attacked the problem head-on: booby-trap the stolen cash so a robbery couldn't pay off, using a pressure squeeze, a tilt switch triggered the instant the pack left the drawer, or a hidden button a teller pressed under duress. Every one of those designs fired the marking charge on the spot, in the lobby, in the robber's own hand — which meant the fix for robbery risked creating a hostage crisis instead, and simply making the trigger more sensitive or more concealed did nothing to move the explosion out of the room.

他们看到了什么

Robeson and Birchfield located the actual danger correctly: it wasn't the marking device, it was WHERE in time its trigger sat. Any trigger a person had to operate under a robber's gun, or any trigger that fired the instant the money was disturbed, necessarily went off inside the blast radius of a hostage. Moving the trigger to a place the robber had no choice but to pass on the way out — the exit itself — meant the device could wait for the one moment in the entire robbery when no hostage stood near the money: after the robber had already left.

那一手

Robeson and Birchfield, both of Atlanta, patented (U.S. Patent 3,564,525, filed September 1967, issued February 16, 1971) a system that moved the trigger out of the teller's hands and out of the lobby entirely: a stationary low-frequency electromagnetic field transmitter positioned near the premises' escape routes, which the dummy currency pack had to be carried through and past by a set distance before a timing circuit began counting down to release tear gas, dye and colored smoke.

为什么管用

The stationary field transmitter at the escape route needs no teller to act under duress and does not fire the instant the pack is disturbed — it only starts its countdown once the pack has been carried a set distance past the transmitter, which means through the door and away from staff and customers. By the time the tear gas, dye and colored smoke actually discharge, the robber is alone outside with cash that is now visibly marked and worthless, which delivers the intended effect — force the robber to abandon or be caught with conspicuously marked money — without ever exposing a bystander to the device meant to catch the person who endangered them.

值了多少

Because the marked pack stayed inert through the robbery itself and only began its countdown once carried past the exit field, the tear gas and dye discharged after the robber had already left the building — protecting hostages while still permanently marking both the stolen cash and the robber. By the time of inventor Harold Robeson's death in 1998, the design he and Birchfield patented was in use, in descendant form, at roughly 5,000 U.S. financial institutions.

什么时候会失灵

The design needs a defensible, physically constrained exit path — a single teller line and a small number of escape routes a stationary field transmitter can reliably cover — and does nothing for a theft where the stolen item can leave by an unpredictable or open route. It also depends on the marked pack passing as ordinary cash at the moment of the handoff: once robbers learn to recognize or specifically reject the marked packs, as later law-enforcement reporting on this technology has documented, the mechanism's power as a primary deterrent erodes even though the underlying delayed-trigger logic still works exactly as designed.

后来呢

The delayed, location-triggered dye pack became the standard bank anti-robbery device across the United States for the rest of the 20th century, later refined by security manufacturers into today's radio-controlled versions; law-enforcement surveys of the technology through the 1970s and 80s credited it as the direct or primary cause of arrest in a majority of the robberies where it deployed, though more recent reporting notes some robbers now instruct tellers to withhold the marked packs, softening its effectiveness as a primary deterrent even as it persists as a widely deployed device.

资料来源

1. [1]US3564525A — Robbery protection system and device for temporarily disabling a robber and visibly marking his locationGoogle Patents / USPTO, 1971patents.google.com
2. [2]Harold Robeson, 72, inventor of the dye packThe Baltimore Sun, 1998baltimoresun.com

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