Business Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Jun. 29, 2013	Jun. 30, 2012	Jun. 29, 2013 segment	Jun. 30, 2012
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Number of operating segments			2
Revenue	$ 135,059	$ 141,697	$ 414,644	$ 404,413
Income from operations	16,428	18,182	52,108	58,930
Test [Member]
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Revenue	110,378	116,338	345,424	327,879
Income from operations	10,878	13,674	39,275	42,141
Sensors [Member]
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Revenue	24,681	25,359	69,220	76,534
Income from operations	$ 5,550	$ 4,508	$ 12,833	$ 16,789