CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($)	6 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net income (loss)	$ 260,500	$ (313,600)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Loss on sale of investments	5,000	0
Depreciation and amortization	151,900	154,100
Unrealized holding gain of investments	3,300	0
Deferred income taxes	7,100	16,500
Income tax benefit of stock options exercised	0	8,000
Stock-based compensation	18,200	12,400
Changes in operating assets and liabilities:
Trade accounts receivable	227,600	(184,000)
Contract assets	216,400	133,100
Inventories	(456,000)	(431,400)
Prepaid expenses and other current assets	(67,900)	(66,300)
Accounts payable	142,700	240,200
Contract liabilities	50,500	321,800
Accrued expenses and taxes	(162,000)	(24,500)
Total adjustments	136,800	179,900
Net cash provided by (used in) operating activities	397,300	(133,700)
Investing activities:
Redemption of investment securities, available-for-sale	2,700	0
Purchase of investment securities, available-for-sale	(75,200)	(15,000)
Sale of investment securities, available-for-sale	72,400	0
Capital expenditures	(7,900)	(68,100)
Purchase of other intangible assets	(6,300)	(1,500)
Net cash used in investing activities	(14,300)	(84,600)
Financing activities:
Line of credit proceeds	0	40,000
Payments for contingent consideration	0	(142,700)
Cash dividend declared and paid	(74,700)	0
Principal payments on note payable	(3,300)	(3,400)
Net cash used in financing activities	(78,000)	(106,100)
Net increase (decrease) in cash and cash equivalents	305,000	(324,400)
Cash and cash equivalents, beginning of year	1,053,100	1,025,100
Cash and cash equivalents, end of period	1,358,100	700,700
Cash paid during the period for:
Income taxes	39,700	16,000
Interest	$ 800	$ 600