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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($)
12 Months Ended
Apr. 30, 2020
Apr. 30, 2019
Significant accounting policies and useful lives    
Amount of impairment losses $ 0  
Allowance for doubtful accounts $ 41,000 $ 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  
Inventory Reserves $ 406,000 $ 332,000
Equipment | Minimum    
Significant accounting policies and useful lives    
Estimated useful lives 3 years  
Equipment | Maximum    
Significant accounting policies and useful lives    
Estimated useful lives 10 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