Business Segments - Schedule of Financial Information Relating to Industry Segments (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2019	Jan. 31, 2018	Apr. 30, 2018
Total net revenue	$ 3,455,000	$ 3,260,000	$ 10,551,000	$ 8,597,000
Total income from operations	832,000	582,000	2,491,000	1,973,000
Total depreciation and amortization	81,000	77,000	248,000	163,000
Total capital expenditures	88,000	16,000	88,000	341,000
Total assets	40,920,000		40,920,000		$ 40,942,000
Security Alarm Products [Member]
Total net revenue	2,735,000	2,715,000	8,103,000	6,683,000
Total income from operations	659,000	452,000	1,972,000	1,534,000
Total depreciation and amortization	37,000	10,000	57,000	28,000
Total capital expenditures	35,000		35,000	260,000
Total assets	5,255,000		5,255,000		4,564,000
Cable & Wiring Tools [Member]
Total net revenue	576,000		1,929,000
Total income from operations	138,000		415,000
Total depreciation and amortization	30,000		92,000
Total capital expenditures
Total assets	2,679,000		2,679,000		2,347,000
Other Products [Member]
Total net revenue	144,000	545,000	519,000	1,914,000
Total income from operations	35,000	130,000	104,000	439,000
Total depreciation and amortization		52,000	55,000	94,000
Total capital expenditures	37,000		37,000
Total assets	842,000		842,000		1,521,000
Corporate General [Member]
Total depreciation and amortization	14,000	15,000	44,000	41,000
Total capital expenditures	16,000	$ 16,000	16,000	$ 81,000
Total assets	$ 32,144,000		$ 32,144,000		$ 32,510,000