Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating activities
Net income	$ (443)	$ (1,268)
Adjustments to reconcile net loss to net cash used in operating activities:
Inventories allowances	(31)	33
Deferred tax expense	(106)	(121)
Depreciation and amortization	211	229
Share-based and stock compensation expense	21	2
Restricted stock unit compensation expense	34	0
Loss on investment in securities	1,146	0
Loss on disposal of property, plant and equipment	0	104
Changes in operating assets and liabilities:
Trade accounts receivable	(2,184)	160
Inventories	(929)	(785)
Prepaid expenses and other current assets	12	368
Other assets	7	(5)
Accounts payable	(1,116)	673
Accrued compensation and related taxes	(76)	(912)
Accrued warranty expense	58	196
Deferred revenue	281	(24)
Accrued other expenses and other current liabilities	(203)	233
Net cash used in operating activitiess	(3,318)	(1,117)
Investing activities
Purchases of property, plant and equipment	(143)	(319)
Investment in securities	(3,333)	0
Proceeds from sale of available-for-sale securities	8,335	0
Net cash provided by (used in) investing activities	4,859	(319)
Financing activities
Proceeds from issuance of common stock	0	183
Cash dividends declared and paid	(273)	(1,235)
Repurchase of common stock	(357)	(97)
Cash used in financing activities	(630)	(1,149)
Net change in cash and cash equivalents	911	(2,585)
Cash and cash equivalents, beginning of period	7,147	10,910
Cash and cash equivalents, end of period	8,058	8,325
Supplemental disclosure
Cash paid for interest	0	0
Income tax paid	0	0
Non-cash financing activity
Cashless exercise of stock options and related conversion of net shares to stockholders' equity	$ 0	$ 27