Business Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 27, 2015 USD ($)	Jun. 28, 2014 USD ($)	Jun. 27, 2015 USD ($) segment	Jun. 28, 2014 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment			2
Revenue	$ 133,912	$ 145,471	$ 420,451	$ 421,224
Income from operations	15,427	17,398	48,993	43,899
Test [Member]
Segment Reporting Information [Line Items]
Revenue	109,484	118,194	346,306	342,602
Income from operations	10,139	11,769	35,256	29,351
Sensors [Member]
Segment Reporting Information [Line Items]
Revenue	24,428	27,277	74,145	78,622
Income from operations	$ 5,288	$ 5,629	$ 13,737	$ 14,548