Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net income (loss)	$ 36,738	$ (6,410)
Adjustments to reconcile net income (loss) to net cash (used in) provided operating activities:
Provision for doubtful accounts	(28)	444
Depreciation and amortization	8,893	9,481
Deferred income taxes	8	22
Loss on disposals of fixed assets	164	2
Gain on sale of Videotel	(53,701)	0
Compensation expense related to stock-based awards and employee stock purchase plan	3,019	2,452
Unrealized currency translation gain	(799)	(290)
Changes in operating assets and liabilities:
Accounts receivable	(1,637)	(1,217)
Inventories	(2,412)	(1,907)
Prepaid expenses, other current assets, and current contract assets	(235)	(232)
Other non-current assets and non-current contract assets	(729)	(1,647)
Accounts payable	(2,331)	(992)
Contract liabilities and long-term contract liabilities	2,229	701
Accrued compensation, product warranty and other current liabilities	(612)	1,364
Other long-term liabilities	(17)	(10)
Net cash (used in) provided by operating activities	(11,450)	1,761
Cash flows from investing activities:
Capital expenditures	(9,335)	(11,463)
Cash paid for acquisition of intangible asset	(71)	(22)
Proceeds from sale of fixed assets	103	0
Proceeds from sale of Videotel, net of cash sold	88,447	0
Purchases of marketable securities	(50,300)	(2,036)
Maturities and sales of marketable securities	4,000	10,019
Net cash provided by (used in) investing activities	32,844	(3,502)
Cash flows from financing activities:
Repayments of long-term debt	(2,597)	(136)
Repayments of term note borrowings	(21,938)	(3,975)
Repayments of line of credit borrowings	(15,000)	0
Proceeds from line of credit borrowings	10,000	0
Proceeds from stock options exercised and employee stock purchase plan	558	477
Sale of treasury stock	0	4,500
Payment of finance lease	(457)
Payment of finance lease		(410)
Net cash (used in) provided by financing activities	(29,434)	456
Effect of exchange rate changes on cash and cash equivalents	(767)	(411)
Net decrease in cash and cash equivalents	(8,807)	(1,696)
Cash and cash equivalents at beginning of period	18,050	34,596
Cash and cash equivalents at end of period	9,243	32,900
Supplemental disclosure of non-cash investing activities:
Changes in accrued other and accounts payable related to property and equipment additions	$ 86	$ 965