Condensed Statements Of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statements Of Comprehensive Income (Loss) [Abstract]
Net sales	$ 2,049	$ 2,146	$ 6,317	$ 5,642
Cost of goods sold	975	951	2,941	2,559
Gross profit	1,074	1,195	3,376	3,083
Operating expenses
Selling and marketing	494	406	1,495	1,242
General and administrative	404	414	1,294	1,370
Research and development	194	176	603	628
Total operating expenses	1,092	996	3,392	3,240
Operating income (loss)	(18)	199	(16)	(157)
Non-operating income (expense)
Interest expense	0	0	(1)	0
Interest income	41	36	126	83
Other income	2	2	7	7
Total non-operating income, net	43	38	132	90
Income (loss) before income tax expense (benefit)	25	237	116	(67)
Provision for (benefit of) income tax	6	50	25	(9)
Net income (loss)	19	187	91	(58)
Other comprehensive income
Change in unrealized value of available-for-sale securities, net of income tax	2	0	10	7
Other comprehensive income	2	0	10	7
Net comprehensive income (loss)	$ 21	$ 187	$ 101	$ (51)
Basic
Net income (loss) per share	$ 0.01	$ 0.06	$ 0.03	$ (0.02)
Weighted average shares	3,395,521	3,395,521	3,395,521	3,395,521
Diluted
Net income (loss) per share	$ 0.01	$ 0.06	$ 0.03	$ (0.02)
Weighted average shares	3,398,533	3,398,238	3,397,385	3,395,521