CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 1,634,000	$ 809,000
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	1,876,000	1,659,000
Provision for doubtful accounts	(159,000)	(15,000)
Deferred taxes	261,000	(27,000)
Foreign currency transaction (gains) losses	(140,000)	139,000
Stock based compensation	701,000	640,000
Unrealized loss on available-for-sale equity security	24,000	0
Realized gain on available-for-sale marketable securities	(3,000)	0
Changes in operating assets and liabilities:
Accounts receivable	(3,594,000)	(1,022,000)
Inventories	(387,000)	(5,260,000)
Other assets	(692,000)	(133,000)
Accounts payable	1,124,000	866,000
Advance customer payments	638,000	(3,000)
Accrued expenses	382,000	(1,906,000)
Net cash provided by (used in) operating activities	1,665,000	(4,253,000)
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from maturities of available-for-sale marketable securities	6,018,000	5,187,000
Proceeds from sales of available-for-sale marketable securities	480,000	0
Purchases of available-for-sale marketable securities	(7,006,000)	(5,604,000)
Additions to equipment and leasehold improvements	(1,079,000)	(851,000)
Additions to patents	(76,000)	(107,000)
Net cash used in investing activities	(1,663,000)	(1,375,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	452,000	330,000
Proceeds from issuance of common stock under Employee Stock Purchase Plan	219,000	258,000
Net cash provided by financing activities	671,000	588,000
Effects of exchange rate changes on cash and cash equivalents	16,000	(7,000)
Net increase (decrease) in cash and cash equivalents	689,000	(5,047,000)
Cash and cash equivalents – beginning of period	6,944,000	10,640,000
Cash and cash equivalents – end of period	$ 7,633,000	$ 5,593,000