PROPERTY, PLANT AND EQUIPMENT (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 194,144	$ 190,732
Accumulated depreciation and amortization	177,330	171,152
Property, Plant and Equipment, Net	16,814	19,580
Capitalized Computer Software, Additions	1,600	2,200
Capitalized Computer Software, Amortization	3,100	1,900
Annual depreciation and amortization	$ 8,500	9,200
Internal Use Software [Domain]
Property, Plant and Equipment [Line Items]
Capitalized Computer Software, Useful Life	3 years
Computer and video equipment and software [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 137,489	133,695
Manufacturing tooling and testbeds [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	4,781	4,209
Office equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	4,957	4,963
Furniture, fixtures and other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	10,133	10,425
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 36,784	$ 37,440