Property, Plant and Equipment

The following is a summary of property and equipment, at cost less accumulated depreciation:



(in thousands)	January 31, 2016			January 25, 2015
Property	$	8,888		$	9,022
Buildings	18,749			18,657
Leasehold improvements	10,182			10,429
Machinery and equipment	141,357			135,956
Enterprise resource planning systems	35,907			26,890
Furniture and office equipment	28,166			33,780
Construction in progress	1,539			1,325
Property, plant and equipment, gross	244,788			236,059
Less accumulated depreciation and amortization	(143,782		)	(120,588		)
Property, plant and equipment, net	$	101,006		$	115,471

As of January 31, 2016 and January 25, 2015, construction in progress consists primarily of machinery and equipment.

During the fiscal year ended January 31, 2016, the Company did not record significant impairment charges.

During the fiscal year ended January 25, 2015, the Company recorded impairment charges against certain property, plant and equipment assets as a result of its strategic decision to reduce its investment in the defense and microwave communications infrastructure market and further reduction of its investment in the optical long-haul markets. These impairment charges relate primarily to limited sales volumes through the remaining life of the assets. In determining the amount of impairment, the Company used a sales comparison method and cost approach to estimate the fair value of property, plant and equipment, and an income approach to estimate the fair value of intangible assets. The Company concluded that the Systems Innovation reporting unit is also the asset group for impairment testing purposes. The categorization and classification of these charges, recorded in fiscal year 2015, are summarized below:



(in thousands)	Machinery and equipment		Furniture and office equipment		Leasehold improvements		Total
Cost of sales	$	2,799	$	10	$	1	$	2,810
Product development and engineering	3,477		33		—		3,510
Selling, general and administrative expenses	5		—		1		6
Total impairment charge	$	6,281	$	43	$	2	$	6,326

During the fiscal year ended January 26, 2014, the Company recorded impairment charges against certain property, plant and equipment assets as a result of its strategic decision to reduce its investment in the optical long-haul market. These impairment charges relate primarily to excess manufacturing capacity. In determining the amount of impairment, the Company used a cost approach to estimate the fair value of test equipment, computer software, leasehold improvements and furniture and fixtures. The sales comparison approach was used to value computer hardware. The Company concluded that the former Advanced Communication reporting unit, which subsequently became part of the Signal Integrity and Timing product group (the Signal Integrity product group since the first quarter of fiscal 2015), is also the asset group for impairment testing purposes. See Note 17. The categorization and classification of these charges, recorded in fiscal year 2014, are summarized below:



(in thousands)	Machinery and equipment		Furniture and office equipment		Leasehold improvements		Total
Cost of sales	$	4,019	$	5	$	317	$	4,341
Product development and engineering	2,173		12		2		2,187
Selling, general and administrative expenses	23		69		222		314
Total impairment charge	$	6,215	$	86	$	541	$	6,842

The net book value of equipment and machinery that are consigned to multiple foundries in China is $5.5 million and $7.6 million as of January 31, 2016 and January 25, 2015, respectively. The net book value of equipment and machinery that are consigned to a foundry in Malaysia is $1.6 million and $2.3 million as of January 31, 2016 and January 25, 2015, respectively.

Depreciation expense was $23.2 million, $21.1 million, and $21.8 million in fiscal years 2016, 2015, and 2014, respectively.