Income Taxes - Deferred Tax Assets and Liabilities (Detail) - USD ($)	Sep. 30, 2017	Sep. 30, 2016
Deferred Tax Assets:
Accrued liabilities and reserves	$ 351,000	$ 331,000
Allowance for doubtful accounts	73,000	70,000
Inventory	778,000	632,000
R&D tax credits carryforwards	155,000	871,000
Stock-based compensation	95,000	140,000
Net operating losses carryforwards	58,000	73,000
Unrealized loss on investments		85,000
Other	48,000	62,000
Gross Deferred Tax Assets	1,558,000	2,264,000
Deferred and Other Tax Liabilities:
Domestic international sales corporation	(839,000)	(577,000)
Percentage of completion	(1,114,000)	(1,158,000)
Property and equipment	(694,000)	(683,000)
Unrealized gain on investments	(332,000)
Unrecognized tax benefits	(150,000)	(150,000)
Other	(30,000)	(12,000)
Gross Deferred and Other Tax Liabilities	(3,159,000)	(2,580,000)
Net Deferred and Other Income Tax Liabilities	$ (1,601,000)	$ (316,000)