Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 24, 2016		Sep. 26, 2015
Cash flows from operating activities:
Net income (loss)	$ 965		$ (1,699)
Reconciliation of net income (loss) to net cash provided by operating activities:
Loss on disposal of assets	37
Loss on disposal of microwave communications equipment business	4		3,232
Operating cash flows of discontinued operations			(1,039)
Depreciation and amortization	8,089		8,533
Share-based compensation expense	5,276		5,081
Deferred income taxes	(1,111)		(1,086)
Asset impairment charge			279
Changes in other accrued liabilities	716		1,624
Changes in other assets	(32)		(522)
Changes in current assets and liabilities, excluding effects from divestitures:
Accounts receivable	3,073		12,860
Inventories	3,551		(5,273)
Other current assets	(411)		2,891
Accounts payable	(2,109)		2,219
Deferred profit	1,970		(1,127)
Income taxes payable	(2,451)		1,804
Accrued compensation, warranty and other liabilities	980		(3,217)
Net cash provided by operating activities	18,547		24,560
Cash flows from investing activities, excluding effects from divestitures:
Purchases of short-term investments	(31,453)		(453)
Sales and maturities of short-term investments	13,654		155
Purchases of property, plant and equipment	(2,797)		(3,687)
Cash received from sale of facility and fixed assets	852
Cash received from sale of microwave communications equipment business			5,339
Investing cash flows of discontinued operations			(74)
Net cash provided by (used in) investing activities	(19,744)		1,280
Cash flows from financing activities:
Cash dividends paid	(4,748)		(4,648)
Issuance (repurchases) of common stock, net	(1,325)		201
Net cash used in financing activities	(6,073)		(4,447)
Effect of exchange rate changes on cash and cash equivalents	1,117		(3,018)
Net increase (decrease) in cash and cash equivalents	(6,153)		18,375
Cash and cash equivalents at beginning of period	115,370	[1]	70,885
Cash and cash equivalents at end of period	109,217		89,260
Supplemental disclosure of cash flow information:
Cash paid (refunded) for income taxes	5,977		(414)
Inventory capitalized as property, plant and equipment	201		220
Dividends declared but not yet paid	1,603		1,567
Capitalized facility under build-to-suit lease			$ 682

[1] Derived from December 26, 2015 audited financial statements