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			Join Date: Jun 2013 
				
				
				
					Posts: 1,294
				 
				
				
				
				
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			I know that this isn't really ethnographic, but some of you guys have been around for hundreds of years, so I thought you might know what it is. 
		
		
		
			It reminds me of the old sound tubes used on Steam Shps where the bridge would communicate with the engine room; am I close?  | 
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