DETAIL OF SELECTED BALANCE SHEET ACCOUNTS (Tables)

3 Months Ended

Dec. 31, 2017

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



	Three months ended December 31,
	2017			2016
Balance at beginning of period	$	179		$	811
Bad debt expense (recovery)	(20		)	(113		)
Uncollectible accounts written off, net of recoveries	(1		)	(28		)
Change due to foreign currency translation	—			(6		)
Balance at end of period	$	158		$	664

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



	December 31, 2017		September 30, 2017
Raw materials, parts and subassemblies, net	$	17,701	$	17,848
Work-in-progress	834		600
Total inventories	$	18,535	$	18,448

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



	December 31, 2017			September 30, 2017
Costs incurred on uncompleted contracts	$	984,882		$	987,164
Estimated earnings	311,391			316,970
	1,296,273			1,304,134
Less: Billings to date	(1,294,017		)	(1,278,746		)
Net underbilled position	$	2,256		$	25,388
Included in the accompanying balance sheets under the following captions:
Costs and estimated earnings in excess of billings on uncompleted contracts	$	38,985		$	51,554
Billings in excess of costs and estimated earnings on uncompleted contracts	(36,729		)	(26,166		)
Net underbilled position	$	2,256		$	25,388

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



	Three months ended December 31,
	2017			2016
Balance at beginning of period	$	3,174		$	4,639
Increase to warranty expense	195			370
Deduction for warranty charges	(478		)	(725		)
Change due to foreign currency translation	(1		)	(54		)
Balance at end of period	$	2,890		$	4,230