Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Cash Flows From Operating Activities:
Net loss	$ (4,028)	$ (5,432)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	200	183
Share-based compensation	628	1,209
Warranty provision	(33)	12
Non-cash lease expense	26	24
Provision for doubtful accounts	(8)	18
Changes in assets and liabilities:
Accounts receivable	1,687	(398)
Inventories	(1,652)	(304)
Prepaid expenses and other current assets	(83)	133
Accounts payable	(42)	(51)
Operating lease liability	(26)	(21)
Customer deposits	1	(43)
Accrued liabilities and other	306	37
Warranty settlement	(1)	(54)
Deferred revenue	(42)	17
Net cash used in operating activities	(3,067)	(4,850)
Cash Flows From Investing Activities:
Purchase of short-term investments	(2,645)	(4,996)
Proceeds from maturities of short-term investments	10,000	10,000
Capital expenditures for property and equipment	(15)	(81)
Investment in long-term deposits	0	(2)
Proceeds from long-term deposits	31	0
Net cash provided by investing activities	7,240	4,852
Cash Flows From Financing Activities:
Proceeds from exercise of stock options	0	75
Net cash provided by financing activities	0	75
Net decrease in cash and cash equivalents	4,173	77
Cash and cash equivalents, beginning of period	5,330	4,937
Cash and cash equivalents, end of period	9,503	5,014
Supplemental Disclosure of Non-Cash Investing
Change in unrealized gain on short-term investments	(94)	(23)
Right-of-use asset and liability recorded during period	0	335
Patents and Trademarks [Member]
Cash Flows From Investing Activities:
Investment in patents and trademarks	$ (131)	$ (69)