F. INTANGIBLE ASSETS (Tables)

12 Months Ended

Dec. 31, 2015

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible assets

	2015
	Gross Amount		Accumulated amortization			Intangible assets, net
	(in thousands)
Patents	$	5,446	$	(1,551	)	$	3,895
Trademarks		14		(9	)		5
Total intangible assets	$	5,460	$	(1,560	)	$	3,900

	2014
	Gross Amount		Accumulated amortization			Intangible assets, net
	(in thousands)
Patents	$	4,968	$	(1,141	)	$	3,827
Trademarks		14		(8	)		6
Total intangible assets	$	4,982	$	(1,149	)	$	3,833

Amortization expense for intangible assets

2016	$	424
2017		424
2018		424
2019		424
2020		424
thereafter		1,780
	$	3,900