CONDENSED CONSOLIDATED STATEMENTS OF INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Net sales	$ 9,988	$ 8,590
Cost of sales	6,560	5,115
Gross profit	3,428	3,475
Operating expenses:
Selling expenses	37	130
General and administrative expenses	1,093	705
Research and development costs	980	1,091
Total operating expenses	2,110	1,926
Operating income	1,318	1,549
Other income (expense):
Interest and miscellaneous income	24	53
Unrealized gain (loss) on marketable equity investments	149	(107)
Interest expense	(120)	(54)
Total other expense	53	(108)
Income before income taxes	1,371	1,441
Provision for income taxes	307	283
Net income	$ 1,064	$ 1,158
Basic net income per share	$ 0.29	$ 0.30
Diluted net income per share	$ 0.28	$ 0.29
Weighted average common shares outstanding:
Basic	3,651,334	3,850,838
Diluted	3,777,118	3,975,063
Common shares outstanding	3,666,319	3,858,251