CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 1,441,000	$ 844,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	634,000	664,000
Non-cash operating lease expense	152,000	137,000
Provision (recovery) for doubtful accounts	30,000	(23,000)
Deferred taxes	122,000	64,000
Foreign currency transaction gains	6,000	(381,000)
Share-based compensation	334,000	272,000
Unrealized (gain) loss on available-for-sale equity security	(17,000)	18,000
Changes in operating assets and liabilities:
Accounts and trade notes receivable	(1,124,000)	1,841,000
Inventories	(721,000)	(2,086,000)
Prepaid expenses and other assets	(73,000)	(111,000)
Accounts payable	2,703,000	1,348,000
Advance customer payments and other	(120,000)	51,000
Accrued expenses	(738,000)	14,000
Operating leases	(211,000)	(200,000)
Net cash provided by operating activities	2,418,000	2,452,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from maturities of available-for-sale marketable securities	2,597,000	3,106,000
Purchases of available-for-sale marketable securities	(2,767,000)	(5,294,000)
Additions to equipment and leasehold improvements	(650,000)	(129,000)
Additions to patents	(34,000)	(17,000)
Net cash used in investing activities	(854,000)	(2,334,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	57,000	85,000
Net cash provided by financing activities	57,000	85,000
Effects of exchange rate changes on cash and cash equivalents	11,000	30,000
Net decrease in cash and cash equivalents	1,632,000	233,000
Cash and cash equivalents – beginning of period	8,399,000	5,836,000
Cash and cash equivalents – end of period	$ 10,031,000	$ 6,069,000