Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 8,586	$ 38,739
Restricted cash - current	525	453
Short-term investments	19,844
Accounts receivable, net of allowance of $235 and $180 at 2022 and 2021, respectively	5,090	5,406
Inventories, net	7,876	4,433
Prepaid expenses and other current assets	1,325	2,356
Total current assets	43,246	51,387
Property and equipment, net	3,831	2,632
Restricted cash	744	952
Operating lease right-of-use assets	5,384	5,736
Prepaid and other non-current assets	208	278
Total assets	53,413	60,985
Current liabilities:
Accounts payable	3,270	4,189
Accrued liabilities	3,306	2,528
Deferred revenue	7,342	6,277
Current portion of operating lease liabilities	373	268
Total current liabilities	14,291	13,262
Long-term deferred revenue	1,654	2,238
Operating lease liabilities	5,488	5,842
Other liabilities	51	218
Total liabilities	21,484	21,560
Series A - Convertible preferred stock:
Convertible preferred stock, Series A, par value $0.001; 22,383 and 22,387 shares outstanding at 2022 and 2021, respectively	5,583	5,584
Stockholders’ equity:
Convertible preferred stock, Series B, par value $0.001; 10,000,000 shares authorized, 5,610,121 shares outstanding at 2022 and 2021	6	6
Common stock, par value $0.001; 300,000,000 shares authorized, 74,874,459 and 74,618,240 shares issued at 2022 and 2021, respectively	75	75
Additional paid in capital	543,438	532,641
Treasury stock, 4,015 shares at 2022 and 2021	(206)	(206)
Accumulated deficit	(516,967)	(498,675)
Total stockholders’ equity	26,346	33,841
Total liabilities and stockholders’ equity	$ 53,413	$ 60,985