Business segment information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 27, 2013	Sep. 28, 2012	Sep. 27, 2013	Sep. 28, 2012
Segment Reporting Information [Line Items]
Total Net sales	$ 94,840	$ 88,233	$ 267,904	$ 282,751
Severance, impairment and other associated costs	2,670	3,851	2,782	5,901
Debt restructuring and related costs	0	814	0	814
Legal reserve	36	0	111	50
Operating profit (loss)	523	(5,762)	3,085	(7,996)
Interest expense, net	(6,231)	(3,754)	(18,119)	(10,099)
Other (expense) income, net	57	948	(2,883)	877
Loss before income taxes	(5,651)	(8,568)	(17,917)	(17,218)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Net sales	94,840	88,233	267,904	282,751
Operating profit (loss) excluding severance, impairment and other associated costs, debt restructuring and related costs and legal reserve costs	3,229	(1,097)	5,978	(1,231)
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Severance, impairment and other associated costs	2,670	3,851	2,782	5,901
Debt restructuring and related costs	0	814	0	814
Legal reserve	36	0	111	50
Network [Member]
Segment Reporting Information [Line Items]
Total Net sales	39,472	39,902	113,757	120,355
Operating profit (loss) excluding severance, impairment and other associated costs, debt restructuring and related costs and legal reserve costs	1,726	2,487	3,980	2,431
Power [Member]
Segment Reporting Information [Line Items]
Total Net sales	28,116	28,932	85,255	92,743
Operating profit (loss) excluding severance, impairment and other associated costs, debt restructuring and related costs and legal reserve costs	2,170	678	5,249	5,056
Wireless [Member]
Segment Reporting Information [Line Items]
Total Net sales	27,252	19,399	68,892	69,653
Operating profit (loss) excluding severance, impairment and other associated costs, debt restructuring and related costs and legal reserve costs	$ (667)	$ (4,262)	$ (3,251)	$ (8,718)