8. Income Taxes (Details 2) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Operating loss carryforwards	$ 313	$ 1,874
R&D tax credit	1,394	1,478
AMT tax credit	179	352
Section 263A costs	252	315
R&D costs	224	335
Amortization	24	24
Unrealized loss	422	0
Asset reserves:
Bad debts	12	12
Inventory allowance	146	182
Accrued expenses:
Non-qualified stock options	112	86
Compensation	140	165
Warranty	764	465
Deferred tax assets	3,982	5,288
Less state valuation allowance	0	(64)
Total deferred tax assets	3,982	5,224
Deferred tax liabilities:
Depreciation	(487)	(338)
Total deferred tax liabilities	(487)	(338)
Net deferred tax assets (before unrealized gain)	3,495	4,886
Deferred tax liability: unrealized gain	0	(1,569)
Net deferred tax assets	$ 3,495	$ 3,317