Condensed Statements Of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statements Of Comprehensive Income (Loss) [Abstract]
Net sales	$ 2,462	$ 2,092	$ 4,363	$ 4,015
Cost of goods sold	1,086	994	1,997	1,918
Gross profit	1,376	1,098	2,366	2,097
Operating expenses
Selling and marketing	364	443	712	901
General and administrative	458	440	901	905
Research and development	283	196	486	413
Total operating expenses	1,105	1,079	2,099	2,219
Operating income (loss)	271	19	267	(122)
Non-operating income
Loss on investment	0	0	0	(3)
Interest expense	0	(1)	0	(1)
Interest income	0	1	2	33
Other income	0	0	0	2
Total non-operating income, net	0	0	2	31
Income (loss) before income tax expense (benefit)	271	19	269	(91)
Provision for (benefit of) income tax	57	1	57	(18)
Net income (loss)	214	18	212	(73)
Other comprehensive loss
Change in unrealized value of available-for-sale securities, net of income tax	(1)	0	(1)	0
Other comprehensive loss	(1)	0	(1)	0
Net comprehensive income (loss)	$ 213	$ 18	$ 211	$ (73)
Basic
Net income (loss) per share	$ 0.06	$ 0.01	$ 0.06	$ (0.02)
Weighted average shares	3,395,521	3,395,521	3,395,521	3,395,521
Diluted
Net income (loss) per share	$ 0.06	$ 0.01	$ 0.06	$ (0.02)
Weighted average shares	3,413,444	3,395,521	3,433,609	3,395,521