Condensed Statements Of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statements Of Comprehensive Income (Loss) [Abstract]
Net sales	$ 1,899	$ 2,049	$ 5,914	$ 6,317
Cost of goods sold	907	975	2,825	2,941
Gross profit	992	1,074	3,089	3,376
Operating expenses
Selling and marketing	417	494	1,318	1,495
General and administrative	420	404	1,325	1,294
Research and development	209	194	622	603
Total operating expenses	1,046	1,092	3,265	3,392
Operating loss	(54)	(18)	(176)	(16)
Non-operating income (expense)
Loss on investment	0	0	(3)	0
Interest expense	(2)	0	(3)	(1)
Interest income	2	41	35	126
Other income	0	2	2	7
Total non-operating income, net	0	43	31	132
Income (loss) before income tax expense (benefit)	(54)	25	(145)	116
Provision for (benefit of) income tax	(8)	6	(26)	25
Net income (loss)	(46)	19	(119)	91
Other comprehensive income
Change in unrealized value of available-for-sale securities, net of income tax	0	2	0	10
Other comprehensive income	0	2	0	10
Net comprehensive income (loss)	$ (46)	$ 21	$ (119)	$ 101
Basic
Net income (loss) per share	$ (0.01)	$ 0.01	$ (0.04)	$ 0.03
Weighted average shares	3,395,521	3,395,521	3,395,521	3,395,521
Diluted
Net income (loss) per share	$ (0.01)	$ 0.01	$ (0.04)	$ 0.03
Weighted average shares	3,395,521	3,398,533	3,395,521	3,397,385