Necm

without internet , without using recorder 
 
how can remote listening be possible?
 
how is it in movies,?
 
thank you...

thank you.. but
 
for example 5 or 2 km maybe farther
 
I think with radio frequency?

I want to know how it works... 
 
I am very curious....
 
 

I have no information...I'm studying this
 
 

@ManosMax13 thank you 
 
@rice guru   is this the same ? 
 

Wait so you don't know who uses the technology you are studying? The only thing I know are radio frequencies. Also check what @rice guru linked, it may be helpful.