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Note 2 - Revenue Recognition (Details Textual) - USD ($)
3 Months Ended
Mar. 31, 2018
Dec. 31, 2017
Maintenance Plan, Service Requirement, Period Subsequent to One Year Anniversary of Invoice 1 year  
Standard Product Warranty, Term 1 year  
Accounts Receivable, Net, Current, Total $ 241,764 $ 137,499
Contract with Customer, Liability, Current $ 38,856 $ 6,663
Minimum [Member]    
Standard Payment Term for Customers 30 days  
Maximum [Member]    
Standard Payment Term for Customers 60 days