Note 12 - Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss (state and foreign)	$ 299	$ 444
Inventories	212	185
Accrued vacation pay and stock-based compensation	184	156
Tax credit carryforwards	81	206
Depreciation of property and equipment		97
Allowance for doubtful accounts	46	47
Accrued warranty	20	20
Acquisition costs	13	15
Other	18	15
Total	873	1,185
Valuation allowance	(241)	(370)
Deferred tax assets	632	815
Deferred tax liabilities:
Net intangible assets	(3,167)	(3,421)
Depreciation of property and equipment	(154)
Deferred tax liabilities	(3,321)	(3,421)
Net deferred tax liabilities	$ (2,689)	$ (2,606)