Consolidated Statements of Cash Flows (unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash Flows From Operating Activities:
Net loss	$ (13,228,000)	$ (5,162,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	219,000	52,000
Product line exit expense	747,000	0
Gain on sale of assets	(11,000)	0
Warranty provision	10,000	19,000
Inventory obsolescence	0	(48,000)
Non-cash lease expense	46,000	60,000
Share-based compensation	3,007,000	1,016,000
Common shares issued for services	239,000	0
Provision for doubtful accounts	46,000	10,000
Changes in assets and liabilities:
Accounts receivable	(798,000)	(307,000)
Inventories	(713,000)	206,000
Prepaid expenses and other current assets	(65,000)	(29,000)
Accounts payable	48,000	376,000
Operating lease liability	(48,000)	(62,000)
Customer deposits	8,000	(193,000)
Accrued liabilities and other	53,000	165,000
Warranty settlement	16,000	0
Deferred revenue	170,000	0
Net cash used in operating activities	(10,254,000)	(3,897,000)
Cash Flows From Investing Activities:
Purchase of short-term investments	(25,009,000)	0
Proceeds from maturities of short-term investments	20,000,000	0
Capital expenditures for property and equipment	(367,000)	(69,000)
Investment in patents and trademarks	(96,000)	(82,000)
Proceeds from long-term deposits	3,000	0
Net cash used in investing activities	(5,469,000)	(151,000)
Cash Flows From Financing Activities:
Sale of common stock and warrants	0	12,400,000
Offering costs paid on sale of common stock and warrants	0	(733,000)
Proceeds from exercise of warrants	12,048,000	10,251,000
Offering costs paid on exercise of warrants	0	(398,000)
Proceeds from exercise of stock options	278,000	515,000
Proceeds from bank note	0	414,000
Repayment of debt	(200,000)	0
Net cash provided by financing activities	12,126,000	22,449,000
Net increase (decrease) in cash and cash equivalents	(3,597,000)	18,401,000
Cash and cash equivalents, beginning of period	16,647,000	16,984,000
Cash and cash equivalents, end of period	13,050,000	35,385,000
Supplemental Disclosure of Non-Cash Investing and Financing Activities:
Change in unrealized gain on short-term investments	$ (2,000)	$ 0