Condensed Consolidated Income Statements - USD ($)	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Net revenue	$ 18,964,000	$ 18,030,000
Cost of goods sold	15,983,000	13,710,000
Gross profit	2,981,000	4,320,000
Operating expenses:
Product engineering and development	845,000	766,000
Selling, general and administrative	3,194,000	2,382,000
Total operating expenses	4,039,000	3,148,000
Operating income (loss)	(1,058,000)	1,172,000
Other income (expense), net:
Interest and dividend income, net of fees	804,000	632,000
Realized and unrealized gains on marketable securities, net	2,193,000	1,317,000
Other		(10,000)
Other income (expense),net	2,997,000	1,939,000
Income before income tax expense	1,939,000	3,111,000
Income tax expense	388,000	622,000
Net income	$ 1,551,000	$ 2,489,000
Basic earnings per common share	$ 0.11	$ 0.17
Diluted earnings per common share	$ 0.11	$ 0.17