REVENUE - Statement of cash flows (Details) - USD ($)	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2018
Revenue
Net income (loss)	$ 642,000	$ (2,015,000)
Contract assets	(1,002,000)
Inventories	(692,000)	377,000
Net cash used in operating activities	(453,000)	$ (186,000)
Balances Without Adoption of ASC 606
Revenue
Net income (loss)	96,000
Inventories	(1,250,000)
Net cash used in operating activities	(453,000)
Effect of Change Higher/(Lower)
Revenue
Net income (loss)	546,000
Contract assets	(1,002,000)
Inventories	$ 558,000