Somebody joked yesterday... a 'phone-call'.
One possibility (not claiming this is how it worked...) Buys cheap throw away cell phone, wires to bomb. Goes in Stadium and leaves vest, backpack, etc.
Goes outside and calls it.
But before he gets in, while arming it, the cell phone gets a call, or he pushes a button accidently on it, causing the speaker to sound (the easiest circuit to tap for trigger pulse is the cellphone ringer and/or speaker).
Tinfoil hats say that there are cell phone blockers in stadiums, but if there are they sure don't block outbound calls. Although I've had my cellphone take a message instead of ring while sitting in a ballpark, I assumed it was just cuz of excess circuit use in the ballpark. You sure see enough people on cell phones in ballparks.
Ok, I'll get back on my meds now...
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That way if they have a bomb, they can blow up alone. Is that rude?
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Great, simple and effective idea.
Just try getting it past the ACLU.
Hell, try it out on the ACLU.