Unaudited Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net loss	$ (4,447)	$ (4,009)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	964	769
Amortization of right-of-use assets	282
Amortization of deferred rent		1
Stock-based compensation expense	129	266
Provision for doubtful accounts, net	40	59
Change of inventory to net realizable value	368	425
Deferred income taxes		(927)
Changes in operating assets and liabilities:
Receivables	251	2,585
Inventories	1,840	(33)
Prepaid expenses and other assets	584	54
Accounts payable	(1,750)	(595)
Accrued liabilities	255	38
Income taxes payable	411	(540)
Deferred product revenue	(44)	(37)
Operating lease liabilities	(281)
Other long-term liabilities		79
Net cash used in operating activities	(1,398)	(1,865)
Cash flows from investing activities:
Purchase of property and equipment	(72)	(130)
Purchase of intangibles	(24)	(98)
Capitalized patent defense costs	(2,298)	(2,383)
Proceeds from maturities and sales of marketable securities	2,011	5,128
Purchases of marketable securities	(7,088)	(1,403)
Net cash provided by (used in) investing activities	(7,471)	1,114
Cash flows from financing activities:
Net proceeds from equity-based compensation programs	16	20
Dividend payments		(583)
Repurchase and cancellation of stock		(147)
Net cash provided by (used in) financing activities	16	(710)
Effect of exchange rate changes on cash and cash equivalents	(6)	(31)
Net decrease in cash and cash equivalents	(8,859)	(1,492)
Cash and cash equivalents at the beginning of the period	11,211	5,571
Cash and cash equivalents at the end of the period	2,352	4,079
Cash paid for income taxes		$ 11