Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 22,877	$ 8,586
Restricted cash - current	569	525
Short-term investments		19,844
Accounts receivable, net of allowance of $169 and $235 at 2023 and 2022, respectively	6,645	5,090
Inventories, net	7,703	7,876
Prepaid expenses and other current assets	1,108	1,325
Total current assets	38,902	43,246
Property and equipment, net	3,590	3,831
Restricted cash	481	744
Operating lease right-of-use assets	5,188	5,384
Prepaid and other non-current assets	154	208
Total assets	48,315	53,413
Current liabilities:
Accounts payable	2,840	3,270
Accrued liabilities	2,920	3,306
Deferred revenue	8,223	7,342
Current portion of operating lease liabilities	399	373
Total current liabilities	14,382	14,291
Long-term deferred revenue	1,639	1,654
Operating lease liabilities	5,282	5,488
Other liabilities	43	51
Total liabilities	21,346	21,484
Series A - Convertible preferred stock:
Convertible preferred stock, Series A, par value $0.001; 22,383 shares outstanding at 2023 and 2022	5,583	5,583
Stockholders’ equity:
Convertible preferred stock, Series B, par value $0.001; 10,000,000 shares authorized, 5,610,121 shares outstanding at 2022		6
Common stock, par value $0.001; 300,000,000 shares authorized, 80,682,586 and 74,874,459 shares issued at 2023 and 2022, respectively	81	75
Additional paid in capital	548,782	543,438
Treasury stock, 4,015 shares at 2023 and 2022	(206)	(206)
Accumulated deficit	(527,271)	(516,967)
Total stockholders’ equity	21,386	26,346
Total liabilities and stockholders’ equity	$ 48,315	$ 53,413