Business Segment Information (Financial Information By Reportable Segment) (Details) (USD $)	12 Months Ended
	Sep. 27, 2014	Sep. 28, 2013	Sep. 29, 2012
Segment Reporting Information [Line Items]
Revenue	$ 564,328,000	$ 569,439,000	$ 542,256,000
Income from Operations	60,256,000	79,955,000	80,511,000
Identifiable Assets	487,408,000	451,277,000	451,277,000
Goodwill	26,123,000	16,624,000
Capital expenditures	20,038,000	29,690,000	15,625,000
Depreciation and amortization	19,279,000	16,589,000	13,782,000
Test [Member]
Segment Reporting Information [Line Items]
Revenue	458,153,000	474,119,000	442,012,000
Income from Operations	39,847,000	60,984,000	58,344,000
Identifiable Assets	392,825,000	360,037,000	357,196,000
Goodwill	24,584,000	15,028,000	14,688,000
Capital expenditures	16,553,000	26,775,000	12,551,000
Depreciation and amortization	16,560,000	14,325,000	11,567,000
Sensors [Member]
Segment Reporting Information [Line Items]
Revenue	106,175,000	95,320,000	100,244,000
Income from Operations	20,409,000	18,971,000	22,167,000
Identifiable Assets	94,583,000	91,240,000	94,081,000
Goodwill	1,539,000	1,596,000	1,551,000
Capital expenditures	3,485,000	2,915,000	3,074,000
Depreciation and amortization	$ 2,719,000	$ 2,264,000	$ 2,215,000