Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating activities
Net loss	$ (2,636)	$ (195)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Inventory allowance	194	(38)
Deferred tax benefit	(878)	(178)
Depreciation and amortization	1,219	921
Share-based compensation expense	148	95
Restricted stock unit compensation expense	105	153
Loss (gain) on sale of available-for-sale securities	0	849
Unrealized (gain) loss on investment in securities	(716)	1,822
Changes in operating assets and liabilities:
Trade accounts receivable	1,757	(197)
Inventories	(2,241)	2,930
Prepaid expenses and other current assets	669	(1,629)
Other assets	(5)	53
Lease liability	90	0
Accounts payable	(285)	(376)
Accrued compensation and related taxes	(743)	650
Accrued warranty expense	(298)	157
Deferred revenue	947	1,138
Accrued other expenses and other current liabilities	187	(867)
Net cash provided by (used in) operating activities	(2,486)	5,288
Investing activities
Purchases of property, plant and equipment	(2,455)	(1,396)
Investment in securities	0	(3,741)
Proceeds from sale of available-for-sale securities	0	8,335
Net cash used in investing activities	(2,455)	3,198
Financing activities
Dividends paid	(1,018)	(1,083)
Repurchase of common stock	(1,041)	(3,282)
Proceeds from issuance of common stock	2	0
Proceeds from debt	425	0
Repayment of debt	(19)	0
Net cash used in financing activities	(1,651)	(4,365)
Net change in cash and cash equivalents	(6,592)	4,121
Cash and cash equivalents, beginning of year	11,268	7,147
Cash and cash equivalents, end of year	4,676	11,268
Supplemental disclosure
Cash paid for income taxes	0	0
Interest paid	10	0
Non-cash financing activity
Restricted stock units issued	$ 147	$ 140