CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 844,000	$ 495,000
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	664,000	663,000
Non-cash operating lease expense	137,000	236,000
Recovery for doubtful accounts	(23,000)	(44,000)
Deferred taxes	64,000	71,000
Foreign currency transaction losses (gains)	(381,000)	70,000
Share-based compensation	272,000	244,000
Unrealized loss on available-for-sale equity security	18,000	1,000
Changes in operating assets and liabilities:
Accounts receivable	1,841,000	2,866,000
Inventories	(2,086,000)	(1,625,000)
Prepaid expenses and other assets	(111,000)	445,000
Accounts payable	1,348,000	(2,353,000)
Advance customer payments	51,000	207,000
Accrued expenses	14,000	(802,000)
Operating lease liabilities	(200,000)	(34,000)
Net cash provided by operating activities	2,452,000	440,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from maturities of available-for-sale marketable securities	3,106,000	1,052,000
Purchases of available-for-sale marketable securities	(5,294,000)	(1,263,000)
Additions to equipment and leasehold improvements	(129,000)	(183,000)
Additions to patents	(17,000)	(32,000)
Net cash used in investing activities	(2,334,000)	(426,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	85,000	59,000
Net cash provided by financing activities	85,000	59,000
Effects of exchange rate changes on cash and cash equivalents	30,000	(6,000)
Net increase in cash and cash equivalents	233,000	67,000
Cash and cash equivalents – beginning of period	5,836,000	9,248,000
Cash and cash equivalents – end of period	$ 6,069,000	$ 9,315,000