CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 606,000	$ 1,634,000
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	2,102,000	1,876,000
Recovery for doubtful accounts	(31,000)	(159,000)
Deferred taxes	107,000	261,000
Foreign currency transaction gains	(112,000)	(140,000)
Share-based compensation	737,000	701,000
Unrealized loss on available-for-sale equity security	10,000	24,000
Realized gain on available-for-sale marketable securities	0	(3,000)
Changes in operating assets and liabilities:
Accounts receivable	2,568,000	(3,594,000)
Inventories	(1,123,000)	(387,000)
Other assets	235,000	(692,000)
Accounts payable	(3,538,000)	1,124,000
Advance customer payments	(50,000)	638,000
Accrued expenses	(1,077,000)	382,000
Operating lease assets and liabilities	482,000	0
Net cash provided by operating activities	916,000	1,665,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from maturities of available-for-sale marketable securities	6,144,000	6,018,000
Proceeds from sales of available-for-sale marketable securities	0	480,000
Purchases of available-for-sale marketable securities	(7,080,000)	(7,006,000)
Additions to equipment and leasehold improvements	(1,065,000)	(1,079,000)
Additions to patents	(88,000)	(76,000)
Net cash used in investing activities	(2,089,000)	(1,663,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	173,000	452,000
Repurchase of common stock	(353,000)	0
Proceeds from issuance of common stock under employee stock purchase plan	203,000	219,000
Net cash provided by financing activities	23,000	671,000
Effects of exchange rate changes on cash and cash equivalents	6,000	16,000
Net increase (decrease) in cash and cash equivalents	(1,144,000)	689,000
Cash and cash equivalents – beginning of period	9,248,000	6,944,000
Cash and cash equivalents – end of period	$ 8,104,000	$ 7,633,000