Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 2,356,980	$ 1,687,641
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,242,357	1,261,446
Loss on the sale of equipment	29,658	17,504
Deferred income taxes	134,000	233,000
Changes in operating assets and liabilities:
Accounts receivable, net	114,813	231,322
Inventories, net	519	624,262
Other current assets	177,001	(134,996)
Accounts payable	(64,644)	(178,703)
Accrued wages and salaries	79,042	6,455
Other accrued expenses	138,512	(55,061)
Unearned revenue and customer deposits	(181,056)	397,323
Net cash provided by operating activities	4,027,182	4,090,193
Cash flows from investing activities:
Capital expenditures	(2,027,860)	(2,081,272)
Proceeds from the sale of equipment	3,730	4,869
Proceeds from certificates of deposit	6,225,000	7,303,000
Purchases of certificates of deposit	(7,719,000)	(7,810,000)
Net cash used in investing activities	(3,518,130)	(2,583,403)
Cash flows from financing activities:
Cash dividends paid	(956,471)	(937,148)
Net cash used in financing activities	(956,471)	(937,148)
Net increase (decrease) in cash and cash equivalents	(447,419)	569,642
Cash and cash equivalents at beginning of year	800,894	231,252
Cash and cash equivalents at end of year	353,475	800,894
Net cash paid for income taxes	840,000	710,456
Supplemental schedule of non-cash investing activities:
Capital expenditures in accounts payable	$ 0	$ 22,995