It is true that in Russia there were electronic mines, they hear footsteps ?

heard that in Russia there were electronic " non-contact " mines that can hear footsteps, distinguished footsteps steps from the animals, from the other noise .And operates without stepping on a mine, when a man approaches her ?After the expiration date of batteries mine itself automatically neutralized .It seems like two generations of such mines are in service with the Russian army.

Why in the US Army code name the enemy - " Charlie "?

Why in the US Army code name the enemy - " Charlie "? I know that the phonetic alphabet adopted in the US Army, " Charlie " is the letter " C" - " C ". But the " enemy " in English - enemy, hostile, opponent in the end. There are no words in the " C ". ..