Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue:
Total Revenue	$ 4,049	$ 3,624	$ 10,952	$ 10,183
Cost of revenue:
Total Cost of revenue	743	602	1,891	2,034
Gross profit	3,306	3,022	9,061	8,149
Operating expenses:
Selling, general and administrative	1,592	1,430	5,118	4,522
Research and development	863	722	2,598	2,266
Total Operating expenses	2,455	2,152	7,716	6,788
Operating income from operations	851	870	1,345	1,361
Other, net	0	0	0	33
Income from operations before income taxes	851	870	1,345	1,394
Income tax expense	0	0	0	4
Net income	$ 851	$ 870	$ 1,345	$ 1,390
Net income per share:
Basic (in dollars per share)	$ 0.16	$ 0.17	$ 0.26	$ 0.27
Diluted (in dollars per share)	$ 0.16	$ 0.17	$ 0.26	$ 0.27
Weighted average number of common shares outstanding:
Basic (in shares)	5,212	5,138	5,200	5,117
Diluted (in shares)	5,244	5,151	5,206	5,121
Product sales [Member]
Revenue:
Total Revenue	$ 1,750	$ 1,120	$ 3,970	$ 4,189
Cost of revenue:
Total Cost of revenue	652	512	1,616	1,764
Royalties [Member]
Revenue:
Total Revenue	2,299	2,504	6,982	5,994
Cost of revenue:
Total Cost of revenue	$ 91	$ 90	$ 275	$ 270