Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net income (loss)	$ (7,694)	$ 505
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation and amortization expense	2,867	2,313
Amortization of right of use of assets	611	563
Share-based compensation expense	136	63
Provision for doubtful accounts, net		82
Change of inventory to net realizable value	850	1,517
Changes in operating assets and liabilities:
Receivables	203	192
Inventories	603	1,155
Prepaid expenses and other assets	(2,485)	(417)
Accounts payable	1,438	1,079
Accrued liabilities	166	(865)
Income taxes receivable	(366)	(7,087)
Deferred product revenue	(69)	(50)
Operating lease liabilities	(631)	(570)
Other long-term liabilities	(23)	538
Net cash used in operating activities	(4,394)	(982)
Cash flows from investing activities:
Capitalized patent defense costs	(7,836)	(6,728)
Purchase of property and equipment	(221)	(284)
Purchase of intangibles	(290)	(205)
Proceeds from maturities and sales of marketable securities	4,004	4,605
Purchase of marketable securities	(4,164)	(2,932)
Net cash used in investing activities	(8,507)	(5,544)
Cash flows from financing activities:
Gross proceeds from issuance of common stock and warrants	10,000	5,275
Costs of issuance of common stock and warrants	(712)	(511)
Proceeds from issuance of short-term notes	2,000
Proceeds from Paycheck Protection Program loan		1,499
Principal payments of long-term debt	(1,098)
Proceeds from equity-based compensation programs	15	14
Net cash provided by financing activities	10,205	6,277
Effect of exchange rate changes on cash and cash equivalents	(36)	(12)
Net increase (decrease) in cash and cash equivalents	(2,732)	(261)
Cash and cash equivalents at the beginning of the year	3,803	4,064
Cash and cash equivalents at the end of the year	1,071	3,803
Supplemental disclosure of cash flow information:
Cash paid for income taxes	107	79
Interest paid	$ 296	$ 244