Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
OPERATING ACTIVITIES
Net loss	$ (1,538)	$ (1,442)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation	281	352
Amortization	61	88
Loss on sale of equipment	10	0
Non-cash interest income on held-to-maturity securities	(433)	(5)
Provision for credit losses, net of recoveries	0	(106)
Deferred income taxes	(5)	38
Stock-based compensation, net of forfeitures	389	224
Changes in operating assets and liabilities:
Accounts receivable	1,039	(4,448)
Inventories	(46)	(45)
Prepaid expenses, other current assets and other non-current assets	(6)	(314)
Accounts payable	(295)	1,159
Accrued liabilities and other non-current liabilities	1,239	360
Net cash provided by (used in) operating activities	696	(4,139)
INVESTING ACTIVITIES
Purchases of equipment and patents	(418)	(206)
Purchases of debt securities	(14,026)	(9,777)
Maturities of debt securities	8,000	500
Net cash used in investing activities	(6,444)	(9,483)
FINANCING ACTIVITIES
Proceeds from exercise of stock options	42	0
Taxes paid on behalf of equity award participants	0	(17)
Net cash provided by (used in) financing activities	42	(17)
Effect of exchange rate fluctuations on cash	(44)	(87)
Net decrease in cash and cash equivalents	(5,750)	(13,726)
Cash and cash equivalents at beginning of period	23,328	37,054
Cash and cash equivalents at end of period	17,578	23,328
Supplemental Cash Flow Information:
Cash income taxes paid, net	$ 12	$ 14