Consolidated Statements Of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 774,000	$ 2,827,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,832,000	2,499,000
Non-cash operating lease expense	828,000	0
Provision (recovery) of doubtful accounts	8,000	(159,000)
Deferred taxes	393,000	371,000
Foreign currency transaction losses (gains)	127,000	(155,000)
Share-based compensation	991,000	936,000
Unrealized loss on available for sale equity security	12,000	37,000
Realized gain on available for sale marketable securities	0	(3,000)
Gain on sale of equipment	(26,000)	0
Changes in operating assets and liabilities:
Accounts and trade notes receivable	(1,170,000)	(4,928,000)
Inventories	(439,000)	(2,845,000)
Prepaid expenses and other assets	539,000	(542,000)
Accounts payable	(1,529,000)	4,266,000
Advance customer payments and other	(49,000)	10,000
Accrued expenses	(856,000)	1,782,000
Operating lease liabilities	(308,000)	0
Net cash provided by operating activities	2,127,000	4,096,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from maturities of available-for-sale marketable securities	7,835,000	8,053,000
Proceeds from sales of available-for-sale marketable securities	0	545,000
Purchases of available-for-sale marketable securities	(12,033,000)	(8,944,000)
Proceeds from sale of equipment	84,000	0
Additions to equipment and leasehold improvements	(1,301,000)	(1,964,000)
Additions to patents	(150,000)	(115,000)
Net cash used in investing activities	(5,565,000)	(2,425,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	248,000	525,000
Tax payments related to shares withheld for share-based compensation plans	(67,000)	(123,000)
Common stock repurchases	(353,000)	0
Proceeds from issuance of common stock under employee stock purchase plan	203,000	219,000
Net cash provided by financing activities	31,000	621,000
Effects of exchange rate changes on cash and cash equivalents	(5,000)	12,000
Net increase (decrease) in cash and cash equivalents	(3,412,000)	2,304,000
Cash and cash equivalents – beginning of period	9,248,000	6,944,000
Cash and cash equivalents – end of period	$ 5,836,000	$ 9,248,000