Condensed Statements Of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statements Of Comprehensive Income (Loss) [Abstract]
Net sales	$ 2,154	$ 1,899	$ 6,517	$ 5,914
Cost of goods sold	950	907	2,947	2,825
Gross profit	1,204	992	3,570	3,089
Operating expenses
Selling and marketing	375	417	1,087	1,318
General and administrative	620	420	1,521	1,325
Research and development	189	209	675	622
Total operating expenses	1,184	1,046	3,283	3,265
Operating income (loss)	20	(54)	287	(176)
Non-operating income
Loss on investment	0	0	0	(3)
Interest expense	(1)	(2)	(1)	(3)
Interest income	2	2	4	35
Other income	0	0	0	2
Total non-operating income, net	1	0	3	31
Income (loss) before income tax expense (benefit)	21	(54)	290	(145)
Provision for (benefit of) income tax	4	(8)	61	(26)
Net income (loss)	17	(46)	229	(119)
Other comprehensive loss
Change in unrealized value of available-for-sale securities, net of income tax	0	0	(1)	0
Other comprehensive loss	0	0	(1)	0
Net comprehensive income (loss)	$ 17	$ (46)	$ 228	$ (119)
Basic
Net income (loss) per share	$ 0.01	$ (0.01)	$ 0.07	$ (0.04)
Weighted average shares	3,395,521	3,395,521	3,395,521	3,395,521
Diluted
Net income (loss) per share	$ 0.00	$ (0.01)	$ 0.07	$ (0.04)
Weighted average shares	3,439,377	3,395,521	3,435,595	3,395,521