Business segment information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 29, 2013	Mar. 30, 2012
Segment Reporting Information [Line Items]
Total Net sales	$ 84,806	$ 94,135
Severance, impairment and other associated costs	19	1,537
Legal reserve	38	0
Operating profit (loss)	950	(2,132)
Interest expense, net	(5,114)	(2,593)
Other (expense) income, net	(2,532)	1,079
Loss before income taxes	(6,696)	(3,646)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Net sales	84,806	94,135
Operating profit (loss) excluding severance, impairment and other associated costs and legal reserve cost	1,007	(595)
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Severance, impairment and other associated costs	19	1,537
Legal reserve	38	0
Network [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Net sales	35,831	38,754
Operating profit (loss) excluding severance, impairment and other associated costs and legal reserve cost	1,332	(873)
Power [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Net sales	27,585	31,690
Operating profit (loss) excluding severance, impairment and other associated costs and legal reserve cost	1,169	2,332
Wireless [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Net sales	21,390	23,691
Operating profit (loss) excluding severance, impairment and other associated costs and legal reserve cost	$ (1,494)	$ (2,054)