During a bomb threat - no cell phones, etc.

[mizzou]

don't use radios/walkies and use cell phones only if near bombs

 

[John Connor]

The bomb squad even has there radios set to inhibit to prevent transmission. They can only receive.

You're not even suppose to use a damn cell phone at a gas station, but I see people do it.

It's not about tones and shit like that, but rather RF energy. What if there was a coil in the bomb's circuitry?

 

[who?]

In zones where new roadways are being blasted there are signs instructing to turn cell phones off. Apparently there's a chance that induced voltage might set off a blasting cap.
The cell phone ringer output could be used to turn a transistor on, the transistor could turn the relay on although it apparently doesn't take much to set off a blasting cap.