Consolidated Statements of Cash Flows - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net income	$ 1,081,100	$ 756,500
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	191,600	45,300
Stock-based compensation	63,400	64,500
Deferred income taxes	467,000	517,900
Change in operating assets and liabilities:
Accounts receivables	(641,100)	(1,798,100)
Inventories	180,200	(492,000)
Prepaid expenses and other assets	(174,900)	(131,900)
Income taxes payable	251,600	25,000
Accounts payable and accrued expenses	(941,100)	(37,000)
Deferred revenue	114,700	0
Total adjustments to net income	(488,600)	(1,806,300)
Net cash provided (used) by operating activities	592,500	(1,049,800)
Cash flows from investing activities:
Purchase of property and equipment	(44,400)	(168,100)
Net cash used by investing activities	(44,400)	(168,100)
Cash flows from financing activities:
Repayments under line-of-credit	(750,000)	0
Repayments of long-term debt	(200,000)	0
Proceeds from exercise of stock options	28,100	0
Net cash used by financing activities	(921,900)	0
Net decrease in cash and cash equivalents	(373,800)	(1,217,900)
Cash and cash equivalents, beginning of period	2,097,300	7,165,100
Cash and cash equivalents, end of period	1,723,500	5,947,200
Supplemental disclosures:
Cash paid during the period for interest	$ 41,900	$ 7,400