CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Net sales	$ 7,961	$ 6,399	$ 15,201	$ 13,314
Cost of sales	5,097	4,150	9,557	8,339
Gross profit	2,864	2,249	5,644	4,975
Operating (income) expenses:
Selling expenses	135	97	277	130
General and administrative expenses	664	633	1,327	1,197
Gain from disposal of equipment				(7)
Research and development costs	397	326	881	735
Total operating expenses	1,196	1,056	2,485	2,055
Operating income	1,668	1,193	3,159	2,920
Interest expense	(63)	(69)	(122)	(89)
Interest and other income	33	93	68	168
Gain on sale of investments		356		356
Income from operations before income taxes	1,638	1,573	3,105	3,355
Income tax expense	(389)	(394)	(751)	(827)
Net income	1,249	1,179	2,354	2,528
Other comprehensive income (loss), net of tax:
Unrealized income (loss) from marketable equity investments	705	(494)	649	(349)
Comprehensive income	$ 1,954	$ 685	$ 3,003	$ 2,179
Basic net income per share:
Net income	$ 0.32	$ 0.28	$ 0.59	$ 0.59
Diluted net income per share:
Net income	$ 0.31	$ 0.28	$ 0.58	$ 0.59
Weighted average common shares outstanding:
Basic	3,950	4,195	3,979	4,263
Diluted	4,053	4,242	4,082	4,303
Common shares outstanding	3,884	4,143	3,884	4,143