Various types of wireless communication systems for masks or helmets can be mounted externally or internally on a mask. Different types of microphones can be employed, for example, a bone-conducting microphone or a directional microphone. Ear speakers mounted at various locations on the mask or helmet can be employed. Wireless communication is with a transceiver mounted in or on a lapel unit, a walkie-talkie, or at a remote location.

 
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> Method and computer program product for monitoring integrity of railroad train

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