Quarterly report pursuant to Section 13 or 15(d)

Note 2 - Summary of Significant Accounting Policies (Details Textual)

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Note 2 - Summary of Significant Accounting Policies (Details Textual)
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2018
USD ($)
Jun. 30, 2017
USD ($)
Jun. 30, 2018
USD ($)
Jun. 30, 2017
USD ($)
Dec. 31, 2017
USD ($)
Jan. 01, 2018
USD ($)
Retained Earnings (Accumulated Deficit), Ending Balance $ (129,589,000)   $ (129,589,000)   $ (105,581,000) [1] $ (105,404,000)
Other Liabilities, Noncurrent, Total 305,000   305,000   327,000 [1] 132,000
Accrued Liabilities, Current, Total $ 5,258,000   $ 5,258,000   4,605,000 [1] 4,623,000
Number of Financial Institutions 1   1      
Allowance for Doubtful Accounts Receivable, Ending Balance $ 253,000   $ 253,000   221,000  
Contract with Customer, Asset, Net, Total 0   0   0  
Contract with Customer, Liability, Total 182,000   182,000   $ 0  
Gross Profit, Total 2,814,000 $ 1,239,000 4,161,000 $ 2,661,000    
Equity Method Investment, Other than Temporary Impairment $ 0   $ 0      
Minimum [Member]            
Warranty Period     1 year      
Maximum [Member]            
Warranty Period     3 years      
Customer Concentration Risk [Member] | Sales Revenue, Net [Member]            
Concentration Risk, Number of Customers 1 3 1 2    
Customer Concentration Risk [Member] | Sales Revenue, Net [Member] | One Customer [Member]            
Concentration Risk, Percentage 13.00%   23.00%      
Customer Concentration Risk [Member] | Sales Revenue, Net [Member] | Three Customers [Member]            
Concentration Risk, Percentage   37.00%        
Customer Concentration Risk [Member] | Sales Revenue, Net [Member] | Two Customers [Member]            
Concentration Risk, Percentage       26.00%    
Customer Concentration Risk [Member] | Accounts Receivable [Member]            
Concentration Risk, Number of Customers     2   2  
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Two Customers [Member]            
Concentration Risk, Percentage     49.00%   57.00%  
Accounting Standards Update 2014-09 [Member]            
Retained Earnings (Accumulated Deficit), Ending Balance [2]           177,000
Other Liabilities, Noncurrent, Total [3]           (195,000)
Accrued Liabilities, Current, Total [4]           $ 18,000
Gross Profit, Total     $ 315,000      
Increase in Change Amount Reported for Accrued and Other Liabilities Due To Separate Disclosure of Change in Other Noncurrent Liabilities [Member] | Quarter Ended June 30, 2017 [Member]            
Prior Period Reclassification Adjustment       $ 53,000    
[1] The condensed consolidated balance sheet as of December 31, 2017 has been derived from the audited consolidated financial statements as of that date.
[2] Change relates to cumulative effect adjustment upon adoption of ASC 606.
[3] Change relates to long-term deferred revenue related to the extended warranties not required to be recorded under ASC 606.
[4] Change relates to future costs associated with extended warranties required to be recorded on adoption of ASC 606.