Inventories (Details) (USD $) In Thousands, unless otherwise specified	Jun. 28, 2013	Dec. 28, 2012
Public Utilities, Inventory [Line Items]
Raw materials and purchased parts	$ 2,258	$ 1,946
Work-in-process	2,056	1,318
Finished goods	7,570	8,945
Inventory, Gross	11,884	12,209
Less: inventory reserves	761	536
Inventory, Net	$ 11,123	$ 11,673