C. DETAIL OF SELECTED BALANCE SHEET ACCOUNTS

Allowance for Doubtful Accounts

Activity in our allowance for doubtful accounts receivable consisted of the following (in thousands):


	Three months ended March 31,						Six months ended March 31,
	2016			2015			2016			2015
Balance at beginning of period	$	1,010		$	1,844		$	746		$	1,577
Bad debt expense		92			186			339			469
Uncollectible accounts written off, net of recoveries		(141	)		(120	)		(114	)		(122	)
Change in foreign currency translation		15			(29	)		5			(43	)
Balance at end of period	$	976		$	1,881		$	976		$	1,881

Inventories:

The components of inventories are summarized below (in thousands):


	March 31, 2016		September 30, 2015
Raw materials, parts and subassemblies, net	$	29,414	$	31,807
Work-in-progress		813		1,084
Total inventories	$	30,227	$	32,891

Cost and Estimated Earnings on Uncompleted Contracts

The components of costs and estimated earnings and related amounts billed on uncompleted contracts are summarized below (in thousands):


	March 31, 2016			September 30, 2015
Costs incurred on uncompleted contracts	$	1,000,967		$	912,237
Estimated earnings		308,608			271,640
		1,309,575			1,183,877
Less: Billings to date		(1,259,161	)		(1,121,141	)
Net underbilled position	$	50,414		$	62,736

Included in the accompanying balance sheets under the following captions:
Costs and estimated earnings in excess of billings on uncompleted contracts – underbilled	$	89,970		$	104,793
Billings in excess of costs and estimated earnings on uncompleted contracts – overbilled		(39,556	)		(42,057	)
Net underbilled position	$	50,414		$	62,736

Warranty Accrual

Activity in our product warranty accrual consisted of the following (in thousands):

	Three months ended March 31,						Six months ended March 31,
	2016			2015			2016			2015
Balance at beginning of period	$	5,105		$	4,480		$	4,930		$	4,557
Increase to warranty expense		832			530			2,158			1,067
Deduction for warranty charges		(1,175	)		(504	)		(2,275	)		(1,028	)
Change in foreign currency translation		25			(131	)		(26	)		(221	)
Balance at end of period	$	4,787		$	4,375		$	4,787		$	4,375