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Note 8 - Bank Debt (Details Textual) - USD ($)
12 Months Ended
Jul. 05, 2019
Jul. 05, 2018
Dec. 31, 2019
Mar. 02, 2021
Dec. 31, 2020
Mar. 02, 2020
Sep. 30, 2019
Line of Credit Facility, Remaining Borrowing Capacity     $ 16,300,000   $ 9,200,000    
J P Morgan Chase Bank [Member] | Term Debt [Member]              
Line of Credit Facility, Maximum Borrowing Capacity           $ 30,000,000 $ 20,000,000
Long-term Debt, Total   $ 6,000,000          
Debt Instrument, Periodic Payment, Total     $ 111,111        
J P Morgan Chase Bank [Member] | Term Debt [Member] | Prime Rate [Member]              
Debt Instrument, Basis Spread on Variable Rate   0.25%          
J P Morgan Chase Bank [Member] | Term Debt [Member] | London Interbank Offered Rate (LIBOR) [Member]              
Debt Instrument, Basis Spread on Variable Rate   2.25%          
J P Morgan Chase Bank [Member] | Term Debt [Member] | Subsequent Event [Member]              
Line of Credit Facility, Maximum Borrowing Capacity       $ 20,000,000      
J P Morgan Chase Bank [Member] | Revolving Credit Facility [Member]              
Line of Credit Facility, Maximum Borrowing Capacity   $ 12,000,000          
Line of Credit Facility, Percent of Eligible Accounts   80.00%          
Line of Credit Facility, Percent of Eligible Progress Billing Accounts   50.00%          
Line of Credit Facility, Percent of Eligible Inventory   50.00%          
Line of Credit Facility, Commitment Fee Percentage   0.25%          
J P Morgan Chase Bank [Member] | Revolving Credit Facility [Member] | Prime Rate [Member]              
Debt Instrument, Basis Spread on Variable Rate 0.25%            
J P Morgan Chase Bank [Member] | Revolving Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member]              
Debt Instrument, Basis Spread on Variable Rate 1.75%            
J P Morgan Chase Bank [Member] | Letter of Credit [Member]              
Line of Credit Facility, Maximum Borrowing Capacity   $ 3,000,000