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## 7 Property, Plant and Equipment 

At December 31, 2013 and 2012, property, plant and equipment were comprised of the following: 

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Depreciation expense was $12.2 million, $12.1 million and $10.8 million in 2013, 2012 and 2011, respectively. 

## 8 Goodwill and Intangible Assets 

The changes in the carrying value of goodwill, all of which is included in our Enterprise Networks division, for the year ended December 31, 2013 are as follows: 

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We evaluate the carrying value of goodwill during the fourth quarter of each year and between annual evaluations if events occur or circumstances change that would more likely than not reduce the fair value of the reporting unit below its carrying amount. When evaluating whether goodwill is impaired, we compare the fair value of the reporting unit to which the goodwill is assigned to the reporting unit’s carrying amount, including goodwill. If the carrying amount of the reporting unit exceeds its fair value, then the amount of the impairment loss is measured. There were no impairment losses recognized during 2013 or 2012. 

Intangible assets are included in other assets in the accompanying Consolidated Balance Sheets and include intangible assets acquired in conjunction with our acquisition of Objectworld Communications Corporation on September 15, 2009, Bluesocket, Inc. on August 4, 2011, and the NSN BBA business on May 4, 2012. 

The following table presents our intangible assets as of December 31, 2013 and 2012: 

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Amortization expense was $2.4 million, $2.0 million and $0.7 million in 2013, 2012 and 2011, respectively. 

