CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Net sales	$ 8,590	$ 7,240
Cost of sales	5,115	4,460
Gross profit	3,475	2,780
Operating expenses:
Selling expenses	130	142
General and administrative expenses	705	663
Research and development costs	1,091	484
Total operating expenses	1,926	1,289
Operating income	1,549	1,491
Other income (expense):
Interest and miscellaneous income	53	35
Interest expense	(54)	(59)
Total other income (expense)	(1)	(24)
Income before income taxes	1,548	1,467
Provision for income taxes	283	363
Net income	1,265	1,104
Other comprehensive income (loss), net of tax:
Unrealized loss from marketable equity investments, net of taxes	(107)	(57)
Comprehensive income	$ 1,158	$ 1,047
Basic and diluted income per share:
Basic net income per share	$ 0.33	$ 0.28
Diluted net income per share	$ 0.32	$ 0.27
Weighted average common shares outstanding:
Basic	3,850,838	4,008,017
Diluted	3,975,063	4,110,414
Common shares outstanding	3,858,251	3,990,995