Statements Of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statements Of Comprehensive Income (Loss) [Abstract]
Net sales	$ 1,780	$ 2,328	$ 3,496	$ 3,998
Cost of goods sold	808	1,004	1,608	1,775
Gross profit	972	1,324	1,888	2,223
Operating expenses
Selling and marketing	401	408	836	785
General and administrative	424	379	956	823
Research and development	222	201	452	422
Total operating expenses	1,047	988	2,244	2,030
Operating income (loss)	(75)	336	(356)	193
Non-operating income
Interest income	24	5	47	13
Other income	3	2	5	5
Total non-operating income	27	7	52	18
Income (loss) before income tax expense (benefit)	(48)	343	(304)	211
Provision for (benefit from) income taxes	(5)	120	(59)	72
Net income (loss)	(43)	223	(245)	139
Other comprehensive income
Change in unrealized value of available-for-sale securities, net of income tax	7	4	6	4
Other comprehensive income	7	4	6	4
Net comprehensive income (loss)	$ (36)	$ 227	$ (239)	$ 143
Basic
Net income (loss) per share	$ (0.01)	$ 0.06	$ (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	$ (0.01)	$ 0.06	$ (0.07)	$ 0.04
Weighted average shares	3,395,521	3,402,527	3,395,521	3,402,731