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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($)
12 Months Ended
Apr. 30, 2016
Apr. 30, 2015
Significant accounting policies and useful lives    
Net sales from contracts having deliveries scheduled over more than one year (as a percent) 0.00% 35.00%
Allowance for doubtful accounts $ 12,000 $ 12,000
Inventory time horizon for excess and obsolete review 12 months  
Individual parts time horizon to review for obsolete inventory 12 months  
Individual parts time horizon to review for excess inventory 12 months  
Advertising costs $ 1,000 4,000
Provided limited warranty period 1 year  
Noncurrent deferred income tax asset $ 592,000 $ 836,000
Accounting Standard Update 2015-17 | Balance sheet adjustment    
Significant accounting policies and useful lives    
Noncurrent deferred income tax asset 171,000  
Current deferred income tax asset $ (171,000)  
Equipment | Minimum    
Significant accounting policies and useful lives    
Estimated useful lives 3 years  
Equipment | Maximum    
Significant accounting policies and useful lives    
Estimated useful lives 5 years  
Buildings and improvements | Minimum    
Significant accounting policies and useful lives    
Estimated useful lives 3 years 6 months  
Buildings and improvements | Maximum    
Significant accounting policies and useful lives    
Estimated useful lives 20 years