CONDENSED STATEMENTS OF CASH FLOWS - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (130,738)	$ (378,897)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation	199,906	212,302
Amortization	9,442	9,574
Stock based compensation	2,893	5,461
Deferred income taxes	12,839
Changes in working capital components:
Trade receivables	158,353	405,542
Inventories	(282,766)	(246,362)
Prepaid expenses and other assets	(25,586)	(29,930)
Income tax receivable	(40,622)	(214,359)
Accounts payable	286,829	111,754
Accrued expenses	(77,854)	(120,476)
Net cash provided by (used in) operating activities	112,696	(245,391)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property, plant, and equipment	(49,004)	(60,417)
Purchases of intangible assets	(15,572)	(7,682)
Purchases of short-term investments	(1,205,000)	(1,225,000)
Proceeds on sale of short-term investments	1,425,000	1,133,000
Net cash provided by (used in) investing activities	155,424	(160,099)
CASH FLOWS FROM FINANCING ACTIVITIES:
Payments on long-term debt	(35,632)	(34,883)
Net cash used in financing activities	(35,632)	(34,883)
NET DECREASE IN CASH AND CASH EQUIVALENTS	232,488	(440,373)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	929,700	1,048,713
CASH AND CASH EQUIVALENTS AT END OF PERIOD	1,162,188	608,340
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Cash paid for interest	17,038	17,786
Cash paid for income taxes, net	$ 7,367	$ 8,564