Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net income	$ 3,232	$ 453
Adjustments to reconcile net income to operating cash flow:
Depreciation and amortization	3,239	3,338
Non-cash interest expense	23	23
Non-cash rent expense	(37)	(17)
Bad debt expense	(6)	7
Deferred revenue	(91)	(97)
Reserve for inventory obsolescence	0	(52)
Stock-based compensation	393	838
Deferred income taxes	841	533
Fair value gain on investment	0	(1,731)
Net gain on sale of investment	0	(1,413)
(Loss) gain on sale of property and equipment	28	(189)
(Increase) decrease in operating assets:
Accounts receivable	(1,304)	(423)
Inventories	(538)	(523)
Refundable income taxes	649	2,067
Prepaid expenses and other current assets	423	(526)
Increase (decrease) in operating liabilities:
Accounts payable	311	710
Accrued expenses	(1,278)	783
Operating lease asset amortization/liability	0	(17)
Accrued income taxes	500	47
Net cash provided by operating activities	6,385	3,811
Cash flows from investing activities:
Purchases of investments	0	(15)
Proceeds from sale of investments	0	1,509
Purchases of property and equipment	(1,895)	(1,178)
Proceeds from sale of property and equipment	5	522
Net cash (used in) provided by investing activities	(1,890)	838
Cash flows from financing activities:
Purchase of treasury stock	(405)	(538)
Repayment of line of credit	0	(3,273)
Net cash used in financing activities	(405)	(3,811)
Net increase in cash and cash equivalents	4,090	838
Cash and cash equivalents at the beginning of the period	3,836	2,998
Cash and cash equivalents at the end of the period	7,926	3,836
Supplemental cash flow information:
Cash paid for income taxes, net of (refunds)	(426)	(1,865)
Cash paid for interest	99	259
Non-cash investing and financing activities
Right-of-use assets recognized at ASU 2016-02 transition	0	944
Operating lease liability recognized at ASU 2016-02 transition	0	997
Increase (decrease) in right-of-use assets and operating lease liabilities	(44)	305
Issuance of common stock under equity incentive plans	$ 522	$ 0