Business Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 29, 2014	Mar. 30, 2013	Mar. 29, 2014 segment	Mar. 30, 2013
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Number of operating segments			2
Revenue	$ 137,343	$ 136,917	$ 275,753	$ 279,585
Income from operations	12,354	15,623	26,501	35,680
Test [Member]
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Revenue	110,885	113,943	224,408	235,046
Income from operations	7,741	12,006	17,582	28,397
Sensors [Member]
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Revenue	26,458	22,974	51,345	44,539
Income from operations	$ 4,613	$ 3,617	$ 8,919	$ 7,283