Business Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 30, 2013	Mar. 31, 2012	Mar. 30, 2013 segment	Mar. 31, 2012
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Number of operating segments			2
Revenue	$ 136,917	$ 129,019	$ 279,585	$ 262,716
Income from operations	15,623	17,199	35,680	40,748
Test [Member]
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Revenue	113,943	102,913	235,046	211,541
Income from operations	12,006	10,694	28,397	28,467
Sensors [Member]
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Revenue	22,974	26,106	44,539	51,175
Income from operations	$ 3,617	$ 6,505	$ 7,283	$ 12,281