Note 2 - Summary of Significant Accounting Policies (Details Textual)		3 Months Ended		6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 18, 2019	Sep. 30, 2019 USD ($) $ / shares shares	Sep. 30, 2018 USD ($)	Jun. 30, 2019	Sep. 30, 2019 USD ($) $ / shares shares	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) $ / shares shares		Jan. 01, 2019 USD ($)
Common Stock, Par or Stated Value Per Share | $ / shares		$ 0.0001			$ 0.0001		$ 0.0001	[1]
Common Stock, Shares Authorized | shares		75,000,000			75,000,000		75,000,000	[1]
Operating Lease, Right-of-Use Asset		$ 456,000			$ 456,000				$ 629,000
Operating Lease, Liability, Total		$ 460,000			$ 460,000				$ 629,000
Number of Financial Institutions		1			1
Accounts Receivable, Allowance for Credit Loss, Ending Balance		$ 543,000			$ 543,000		$ 284,000
Deferred Income		579,000			579,000
Contract with Customer, Asset, after Allowance for Credit Loss, Total		0			0		0
Contract with Customer, Liability, Total		470,000			470,000		$ 686,000
Capitalized Contract Cost, Net, Total		198,000	$ 0		198,000	$ 0
Capitalized Contract Cost, Amortization		30,000	0		30,000	0
Equity Method Investment, Other than Temporary Impairment		$ 0	$ 0		$ 0	$ 0
Minimum [Member]
Warranty Period				1 year
Maximum [Member]
Warranty Period				3 years
Customer Concentration Risk [Member] | Revenue Benchmark [Member]
Concentration Risk, Number of Customers		2	3		1	1
Concentration Risk, Percentage			42.00%
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | One Customer [Member]
Concentration Risk, Percentage					17.00%	21.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member]
Concentration Risk, Number of Customers					4		3
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Four Customers [Member]
Concentration Risk, Percentage					67.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Three Customers [Member]
Concentration Risk, Percentage							54.00%
Reverse Stock Split [Member]
Stockholders' Equity Note, Stock Split, Conversion Ratio	100

[1] The condensed consolidated balance sheet as of December 31, 2018 has been derived from the audited consolidated financial statements as of that date.