Condensed Income Statements (Unaudited) - USD ($)	3 Months Ended
	Jul. 31, 2019	Jul. 31, 2018
Income Statement [Abstract]
Net Sales	$ 3,552,000	$ 3,429,000
Less: Cost of Goods Sold	(1,769,000)	(1,801,000)
Gross Profit	1,783,000	1,628,000
Operating Expenses:
General and Administrative	297,000	286,000
Sales	557,000	555,000
Engineering	14,000	9,000
Rent Paid to Related Parties	5,000	5,000
Total Operating Expenses	873,000	885,000
Income From Operations	910,000	773,000
Other Income (Expense)
Other	1,000	3,000
Dividend and Interest Income	193,000	193,000
Gain (Loss) on Sale of Investments	49,000	(68,000)
Total Other Income	243,000	128,000
Income Before Provisions for Income Taxes	1,153,000	901,000
Provisions for Income Taxes
Current Expense	294,000	247,000
Deferred tax expense (benefit)	(7,000)	37,000
Total Income Tax Expense	287,000	284,000
Net Income	$ 866,000	$ 617,000
Basic Earnings Per Share of Common Stock	$ 0.17	$ 0.12
Diluted Earnings Per Share of Common Stock	$ 0.17	$ 0.12
Weighted Average Number of Common Shares Outstanding	4,956,389	4,967,580
Weighted Average Number of Shares Outstanding (Diluted)	4,976,889	4,988,080