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+1
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well u know in spys they have these headphones and when some is far away they can here them by putting on the headphones what ever u call them

off-topic
 Sep 5, 2017
 #1
avatar+590 
0

Walkie Talkie? Headset? I don't really know. 

 Sep 5, 2017
 #2
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0

Sound or voice "Amplifiers" ??!!.

 Sep 5, 2017
 #3
avatar+1002 
+1

Theres so many different kinds of those....

Here i found this website, maybe it will help? 

http://sciencing.com/types-listening-devices-spying-8135997.html

 Sep 5, 2017

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