8. Income Taxes (Details 2) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Operating loss carryforwards	$ 1,347	$ 313
R&D tax credit	1,678	1,394
AMT tax credit	72	179
Section 263A costs	294	252
R&D costs	110	224
Amortization	24	24
Unrealized loss	252	422
Asset reserves:
Bad debts	11	12
Inventory allowance	187	146
Accrued expenses:
Non-qualified stock options	132	112
Compensation	132	140
Warranty	904	764
Deferred tax assets	5,143	3,982
Less state valuation allowance	0	0
Total deferred tax assets	5,143	3,982
Deferred tax liabilities:
Depreciation	(770)	(487)
Total deferred tax liabilities	(770)	(487)
Net deferred tax assets (before unrealized gain)	4,373	3,495
Deferred tax liability: unrealized gain	0	0
Net deferred tax assets	$ 4,373	$ 3,495