Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating activities
Net loss	$ (694)	$ (1,192)
Adjustments to reconcile net loss to net cash provided by operating activities:
Inventories allowances	289	38
Depreciation and amortization	298	320
Share-based compensation expense-stock options	32	30
Share-based compensation expense-restricted stock units	103	21
(Gain) loss on investment in securities	(205)	306
Changes in operating assets and liabilities:
Trade accounts receivable	1,900	(626)
Inventories	(1,359)	2,538
Prepaid expenses and other current assets	57	(69)
Other assets	(6)	28
Lease liability	(4)	23
Accounts payable	299	(474)
Accrued compensation and related taxes	(315)	(226)
Accrued warranty expense	(73)	(149)
Deferred revenue	(138)	424
Accrued other expenses and other current liabilities	(145)	(77)
Net cash provided by operating activities	39	915
Investing activities
Purchases of property, plant and equipment	(1,031)	(131)
Net cash used in investing activities	(1,031)	(131)
Financing activities
Cash dividends paid	(250)	(252)
Repurchase of common stock	0	(243)
Proceeds from credit facilities	800	0
Repayment of note payable	(21)	(19)
Net cash provided by (used in) financing activities	529	(514)
Net change in cash and cash equivalents	(463)	270
Cash and cash equivalents, beginning of period	6,826	4,676
Cash and cash equivalents, end of period	6,363	4,946
Supplemental disclosure
Cash paid for interest	4	5
Non-cash financing activity
Common stock issued under restricted stock units	$ 84	$ 0