CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 3,591,000	$ 1,441,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	569,000	634,000
Non-cash operating lease expense	136,000	152,000
Provision for doubtful accounts	30,000	30,000
Deferred taxes	18,000	122,000
Foreign currency transaction (gains) losses	(33,000)	6,000
Share-based compensation	353,000	334,000
Unrealized loss (gain) on available-for-sale equity security	2,000	(17,000)
Changes in operating assets and liabilities:
Accounts receivable	(2,480,000)	(1,124,000)
Inventories	(2,624,000)	(721,000)
Prepaid expenses and other assets	(363,000)	(73,000)
Accounts payable	2,082,000	2,703,000
Advance customer payments and other	486,000	(120,000)
Accrued expenses	(798,000)	(738,000)
Operating leases	(203,000)	(211,000)
Net cash provided by operating activities	766,000	2,418,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from maturities of available-for-sale marketable securities	3,184,000	2,597,000
Purchases of available-for-sale marketable securities	(7,077,000)	(2,767,000)
Additions to equipment and leasehold improvements	(491,000)	(650,000)
Additions to patents	(29,000)	(34,000)
Net cash used in investing activities	(4,413,000)	(854,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	183,000	57,000
Tax payments for shares withheld related to stock option exercises	(1,000)	0
Net cash provided by financing activities	182,000	57,000
Effects of exchange rate changes on cash and cash equivalents	7,000	11,000
Net (decrease) increase in cash and cash equivalents	(3,458,000)	1,632,000
Cash and cash equivalents – beginning of period	13,684,000	8,399,000
Cash and cash equivalents – end of period	$ 10,226,000	$ 10,031,000