Income Taxes - Deferred Income Tax Assets and Liabilities (Detail) - USD ($)	Sep. 30, 2020	Sep. 30, 2019
Deferred Tax Assets:
Accrued liabilities and reserves	$ 340,000	$ 344,000
Allowance for doubtful accounts	98,000	104,000
Inventory	369,000	98,000
Stock-based compensation	81,000	82,000
Net operating losses carryforwards	5,000	7,000
Gross Deferred Income Tax Assets	893,000	635,000
Deferred and Other Tax Liabilities:
Domestic international sales corporation	(329,000)	(464,000)
Percentage of completion		(2,048,000)
Property and equipment	(1,158,000)	(1,080,000)
Unrealized gain on investment	(2,000)	(265,000)
Unrecognized tax benefits	(150,000)	(150,000)
Gross Deferred and Other Income Tax Liabilities	(1,639,000)	(4,007,000)
Net Deferred and Other Income Tax Assets (Liabilities)	$ (746,000)	$ (3,372,000)