Condensed Consolidated Statements of Cash Flows - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net (loss) income	$ (196,300)	$ 1,081,100
Adjustment to reconcile net income to net cash (used) provided by operating activities:
Depreciation and amortization	206,500	191,600
Stock-based compensation	59,600	63,400
Deferred income taxes	(69,400)	467,000
Change in operating assets and liabilities:
Accounts receivable	205,900	(641,100)
Inventories	352,200	180,200
Prepaid expenses and other assets	(42,000)	(174,900)
Income taxes payable		251,600
Accounts payable and accrued expenses	(622,200)	(941,100)
Deferred revenue		114,700
Total adjustments to net income	90,600	(488,600)
Net cash (used) provided by operating activities	(105,700)	592,500
Cash flows from investing activities:
Purchase of property and equipment		(44,400)
Net cash used by investing activities		(44,400)
Cash flows from financing activities:
Repayments under line-of-credit		(750,000)
Repayments of long-term debt	(200,000)	(200,000)
Proceeds from exercise of stock options	88,400	28,100
Net cash used by financing activities	(111,600)	(921,900)
Net decrease in cash and cash equivalents	(217,300)	(373,800)
Cash and cash equivalents, beginning of period	4,113,800	2,097,300
Cash and cash equivalents, end of period	3,896,500	1,723,500
Supplemental disclosures:
Cash paid during the period for interest	$ 17,800	$ 41,900