Condensed Income Statements (Unaudited) - USD ($)	3 Months Ended
	Jul. 31, 2018	Jul. 31, 2017
Income Statement [Abstract]
Net Sales	$ 3,429,000	$ 2,248,000
Less: Cost of Goods Sold	(1,801,000)	(1,095,000)
Gross Profit	1,628,000	1,153,000
Operating Expenses:
General and Administrative	286,000	229,000
Sales	555,000	416,000
Engineering	9,000	13,000
Rent Paid to Related Parties	5,000	5,000
Total Operating Expenses	855,000	663,000
Income From Operations	773,000	490,000
Other Income (Expense)
Other	3,000	3,000
Dividend and Interest Income	193,000	279,000
Gain (Loss) on Sales of Assets		4,000
Gain (Loss) on Sale of Investments	(68,000)	(38,000)
Total Other Income (Expense)	128,000	248,000
Income Before Provisions for Income Taxes	901,000	738,000
Provisions for Income Taxes
Current Expense	247,000	213,000
Deferred tax expense (benefit)	37,000	7,000
Total Income Tax Expense	284,000	220,000
Net Income	$ 617,000	$ 518,000
Basic Earnings Per Share of Common Stock	$ 0.12	$ 0.1
Diluted Earnings Per Share of Common Stock	$ 0.12	$ 0.1
Weighted Average Number of Common Shares Outstanding	4,967,580	4,945,092
Weighted Average Number of Shares Outstanding (Diluted)	4,988,080	4,965,592