Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 19,818	$ 8,586
Restricted cash - current	525	525
Short-term investments		19,844
Accounts receivable, net of allowance of $672 and $235 at 2023 and 2022, respectively	3,822	5,090
Inventories, net	8,426	7,876
Prepaid expenses and other current assets	676	1,325
Total current assets	33,267	43,246
Property and equipment, net	3,304	3,831
Restricted cash	219	744
Operating lease right-of-use assets	4,982	5,384
Prepaid and other non-current assets	137	208
Total assets	41,909	53,413
Current liabilities:
Accounts payable	3,190	3,270
Accrued liabilities	2,972	3,306
Deferred revenue	6,657	7,342
Current portion of operating lease liabilities	428	373
Total current liabilities	13,247	14,291
Long-term deferred revenue	1,637	1,654
Operating lease liabilities	5,062	5,488
Other liabilities	43	51
Total liabilities	19,989	21,484
Series A - Convertible preferred stock:
Convertible preferred stock, Series A, par value $0.001; 22,358 and 22,383 shares outstanding at 2023 and 2022, respectively	5,577	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, 80,949,697 and 74,874,459 shares issued at 2023 and 2022, respectively	81	75
Additional paid in capital	554,148	543,438
Treasury stock, 4,015 shares at 2023 and 2022	(206)	(206)
Accumulated deficit	(537,680)	(516,967)
Total stockholders’ equity	16,343	26,346
Total liabilities and stockholders’ equity	$ 41,909	$ 53,413