Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities
Net income	$ (1,318)	$ (443)
Adjustments to reconcile net loss to net cash used in operating activities:
Inventories allowances	19	(31)
Deferred tax benefit	(355)	(106)
Depreciation and amortization	256	211
Share-based compensation expense	31	21
Restricted stock unit compensation expense	41	34
(Gain) loss on investment in securities	(592)	1,146
Changes in operating assets and liabilities:
Trade accounts receivable	676	(2,184)
Inventories	(715)	(929)
Prepaid expenses and other current assets	(143)	12
Other assets	1	7
Accounts payable	602	(1,116)
Accrued compensation and related taxes	(951)	(76)
Accrued warranty expense	(88)	58
Deferred revenue	296	281
Accrued other expenses and other current liabilities	(68)	(203)
Net cash used in operating activities	(2,308)	(3,318)
Investing activities
Purchases of property, plant and equipment	(829)	(143)
Investment in securities	0	(3,333)
Proceeds from sale of available-for-sale securities	0	8,335
Net cash (used in) provided by investing activities	(829)	4,859
Financing activities
Proceeds from issuance of common stock	2	0
Cash dividends declared and paid	(256)	(273)
Repurchase of common stock	(337)	(357)
Net cash used in financing activities	(591)	(630)
Net change in cash and cash equivalents	(3,728)	911
Cash and cash equivalents, beginning of period	11,268	7,147
Cash and cash equivalents, end of period	7,540	8,058
Supplemental disclosure
Cash paid for interest	0	0
Income tax paid	0	0
Non-cash financing activity
Restricted stock units issued	0	0
Cashless exercise of stock options and related conversion of net shares to stockholders' equity	$ 0	$ 0