Consolidated Income Statements - USD ($)	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Net revenue	$ 85,278,000	$ 77,420,000
Cost of goods sold	67,100,000	58,467,000
Gross profit	18,178,000	18,953,000
Operating expenses:
Product engineering and development	4,278,000	3,061,000
Selling, general and administrative	13,199,000	10,356,000
Total operating expenses	17,477,000	13,417,000
Operating income	701,000	5,536,000
Other income (expense), net:
Interest and dividend income, net of fees	1,762,000	2,321,000
Realized and unrealized gains (losses) on marketable securities, net	4,171,000	(1,160,000)
Other	0	(16,000)
Other income (expense),net	5,933,000	1,145,000
Income before income tax expense	6,634,000	6,681,000
Income tax expense	829,000	1,150,000
Net income	$ 5,805,000	$ 5,531,000
Basic earnings per common share	$ 0.40	$ 0.38
Diluted earnings per common share	$ 0.39	$ 0.38