STATEMENTS OF CASH FLOWS - USD ($)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Operating activities:    
Net income $ 7,529,920 $ 2,050,366
Adjustments to reconcile net income to net cash provided by operating activities:    
Bad debt expense 3,553 (108,852)
Provision for excess and obsolete inventory 51,089 62,069
Depreciation and amortization 223,942 149,056
Excess tax benefit on the exercise of stock options (1,728,595) (165,228)
Stock-based compensation 1,220,118 724,063
Impairment of intangible assets 55,433  
Loss on sale of investments 3,575  
Changes in operating assets and liabilities:    
Accounts receivable (1,906,971) 130,721
Inventory (308,409) (847,576)
Prepaid expenses and other current assets (31,977) (154,912)
Other assets (113,959) (15,433)
Prepaid income taxes 1,775,568 (48,188)
Deferred income taxes (16,116) (167,305)
Accounts payable 376,293 201,693
Accrued payroll and benefits 43,350 589,536
Other accrued liabilities (35,103) (14,997)
Warranty reserve 6,156 15,923
Deferred revenue 501,463 186,172
Other   (1,388)
Net cash provided by operating activities 7,649,330 2,585,720
Investing activities:    
Purchases of investments   (7,951,497)
Proceeds from sale of investments 253,370 255,109
Purchases of property and equipment (298,723) (583,977)
Capitalized intangible assets (16,116) (22,311)
Net cash used in investing activities (61,469) (8,302,676)
Financing activities:    
Proceeds from stock option and warrant exercises 597,508 105,000
Income tax benefits credited to equity 1,728,595 165,228
Repayment of officer note payable   (6,333)
Proceeds from the issuance of common stock pursuant to initial public offering   14,490,000
Payment of initial public offering costs   (2,044,348)
Net cash provided by financing activities 2,326,103 12,709,547
Net increase in cash and cash equivalents 9,913,964 6,992,591
Cash and cash equivalents, beginning of year 9,454,150 2,461,559
Cash and cash equivalents, end of year 19,368,114 9,454,150
Supplemental disclosure of cash flow information:    
Cash paid for income taxes $ 2,702,000 $ 1,182,430