INCOME TAXES - Components of the net deferred income tax asset (Details) - USD ($)	Apr. 30, 2020	Apr. 30, 2019
INCOME TAXES
Net operating loss carryforwards	$ 19,000	$ 226,000
Inventory valuation reserve	109,000	89,000
Loss on equity and impairment in investee	301,000	301,000
Tax credit carryforward		34,000
Adjustments required by change in method of accounting as a result of adopting ASC 606		(31,000)
Cost of sales adjustment from ASC 606	15,000	163,000
Depreciation expense	(171,000)	(111,000)
Uniform capitalization		19,000
Right-of-use asset	(538,000)
Lease liability	609,000
Bad debt reserve	11,000	3,000
Warranty reserve	5,000	9,000
Accrued vacation	35,000	7,000
Accrued bonuses	65,000	42,000
Accrued commissions	15,000	16,000
Claims reserve	7,000	7,000
Stock compensation	105,000	76,000
Deferred rent		55,000
Other	2,000
Gross deferred income tax asset	589,000	905,000
Less: valuation allowance	$ (589,000)	(871,000)
Net deferred income tax assets		$ 34,000