Business Segments - Schedule of Financial Information Relating to Industry Segments (Details) - USD ($)	3 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Apr. 30, 2020
Total net revenue	$ 4,047,000	$ 3,552,000
Total income from operations	1,186,000	910,000
Total depreciation and amortization	86,000	89,000
Total capital expenditures	95,000	169,000
Total assets	47,349,000		$ 43,762,000
Security Alarm Products [Member]
Total net revenue	3,114,000	2,830,000
Total income from operations	912,000	725,000
Total depreciation and amortization	22,000	23,000
Total capital expenditures	93,000	169,000
Total assets	7,391,000		7,150,000
Cable & Wiring Tools [Member]
Total net revenue	800,000	536,000
Total income from operations	235,000	137,000
Total depreciation and amortization	31,000	31,000
Total capital expenditures
Total assets	3,152,000		2,684,000
Other Products [Member]
Total net revenue	133,000	186,000
Total income from operations	39,000	48,000
Total depreciation and amortization	12,000	20,000
Total capital expenditures	2,000
Total assets	440,000		724,000
Corporate General [Member]
Total depreciation and amortization	21,000	15,000
Total capital expenditures
Total assets	$ 36,366,000		$ 33,204,000