Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 17,633	$ 19,818
Restricted cash - current	525	525
Accounts receivable, net of allowance of $609 and $672 at 2024 and 2023, respectively	3,953	3,822
Inventories, net	8,252	8,426
Prepaid expenses and other current assets	845	676
Total current assets	31,208	33,267
Property and equipment, net	3,164	3,304
Restricted cash	88	219
Operating lease right-of-use assets	4,876	4,982
Prepaid and other non-current assets	116	137
Total assets	39,452	41,909
Current liabilities:
Accounts payable	3,307	3,190
Accrued liabilities	3,164	2,972
Deferred revenue	5,938	6,657
Current portion of operating lease liabilities	443	428
Total current liabilities	12,852	13,247
Long-term deferred revenue	1,581	1,637
Operating lease liabilities	4,945	5,062
Other liabilities	43	43
Total liabilities	19,421	19,989
Series A - Convertible preferred stock:
Convertible preferred stock, Series A, par value $0.001; 10,000,000 shares authorized, 21,908 and 22,358 shares outstanding at 2024 and 2023	5,464	5,577
Stockholders’ equity:
Common stock, par value $0.001; 300,000,000 shares authorized, 82,132,777 and 80,949,697 shares issued at 2024 and 2023, respectively	82	81
Additional paid in capital	556,878	554,148
Treasury stock, 4,015 shares at 2024 and 2023	(206)	(206)
Accumulated deficit	(542,187)	(537,680)
Total stockholders’ equity	14,567	16,343
Total liabilities and stockholders’ equity	$ 39,452	$ 41,909