Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (6,179)	$ (3,893)
Adjustments to reconcile net loss to net cash used in operating activities:
Provision for doubtful accounts	(65)	28
Depreciation and amortization	3,527	3,050
Deferred income taxes	16	9
Loss on disposals of fixed assets	56	0
Compensation expense related to stock-based awards and employee stock purchase plan	874	853
Unrealized currency translation loss	47	40
Changes in operating assets and liabilities:
Accounts receivable	944	(91)
Inventories	(3,117)	(558)
Prepaid expenses, other current assets and current contract assets	(891)	(651)
Other non-current assets and non-current contract assets	(705)	(836)
Accounts payable	2,627	1,067
Contract liabilities and long-term contract liabilities	3,526	1,094
Accrued compensation, product warranty and other	(1,719)	(1,303)
Other long-term liabilities and long-term operating lease liabilities	(15)	(6)
Net cash used in operating activities	(1,074)	(1,197)
Cash flows from investing activities:
Capital expenditures	(3,027)	(3,189)
Cash paid for acquisition of intangible asset	(25)	0
Purchases of marketable securities	0	(1,026)
Maturities and sales of marketable securities	0	6,013
Net cash (used in) provided by investing activities	(3,052)	1,798
Cash flows from financing activities:
Repayments of long-term debt	(31)	(44)
Repayments of term note borrowings	0	(2,825)
Proceeds from stock options exercised and employee stock purchase plan	314	0
Sale of treasury stock	0	4,500
Payment of finance lease	(152)
Payment of finance lease		107
Net cash provided by financing activities	131	1,524
Effect of exchange rate changes on cash and cash equivalents	204	1,047
Net (decrease) increase in cash and cash equivalents	(3,791)	3,172
Cash and cash equivalents at beginning of period	18,050	34,596
Cash and cash equivalents at end of period	14,259	37,768
Supplemental disclosure of non-cash investing activities:
Changes in accrued other and accounts payable related to property and equipment additions	$ 161	$ 537