ACCRUED LIABILITIES (Details) - USD ($)	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019
Employee related expenses:
Accrued payroll	$ 454,000	$ 286,000
Accrued payroll taxes	36,000	22,000
Accrued employee benefits	252,000	165,000
Total employee related expenses	742,000	473,000
Other, including interest:
Warranty reserve	20,000	22,000
Property taxes	38,000	20,000
Deferred rent		206,000
Other	99,000	103,000
Total other	157,000	351,000
Total accrued liabilities	899,000	824,000
Changes in warranty reserve
Balance, May 1	22,000	300,000
Credit memos issued	(194,000)	(212,000)
Provision for warranty accrual	192,000	(66,000)
Balance, April 30	$ 20,000	$ 22,000