UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Beginning balance (shares) at Apr. 30, 2020		12,726,728
Beginning balance at Apr. 30, 2020	$ 5,318	$ 13	$ 77,978	$ (72,673)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	120		120
Issuance of common stock on exercise of stock options (in shares)		1,160
Net income	75			75
Ending balance (shares) at Jul. 31, 2020		12,727,888
Ending balance at Jul. 31, 2020	5,513	$ 13	78,098	(72,598)
Beginning balance (shares) at Apr. 30, 2020		12,726,728
Beginning balance at Apr. 30, 2020	5,318	$ 13	77,978	(72,673)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	76
Ending balance (shares) at Oct. 31, 2020		13,368,545
Ending balance at Oct. 31, 2020	6,893	$ 13	79,477	(72,597)
Beginning balance (shares) at Jul. 31, 2020		12,727,888
Beginning balance at Jul. 31, 2020	5,513	$ 13	78,098	(72,598)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	85		85
Issuance of common stock on exercise of stock options (in shares)		640,657
Issuance of common stock on exercise of stock options	1,294		1,294
Net income	1			1
Ending balance (shares) at Oct. 31, 2020		13,368,545
Ending balance at Oct. 31, 2020	6,893	$ 13	79,477	(72,597)
Beginning balance (shares) at Apr. 30, 2021		13,414,066
Beginning balance at Apr. 30, 2021	7,428	$ 13	79,945	(72,530)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	280		280
Issuance of common stock on exercise of stock options (in shares)		1,000
Issuance of common stock on exercise of stock options	2		2
Net income	(172)			(172)
Ending balance (shares) at Jul. 31, 2021		13,415,066
Ending balance at Jul. 31, 2021	7,538	$ 13	80,227	(72,702)
Beginning balance (shares) at Apr. 30, 2021		13,414,066
Beginning balance at Apr. 30, 2021	7,428	$ 13	79,945	(72,530)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	105
Ending balance (shares) at Oct. 31, 2021		13,496,144
Ending balance at Oct. 31, 2021	8,071	$ 14	80,482	(72,425)
Beginning balance (shares) at Jul. 31, 2021		13,415,066
Beginning balance at Jul. 31, 2021	7,538	$ 13	80,227	(72,702)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	134		134
Issuance of common stock on exercise of stock options (in shares)		81,078
Issuance of common stock on exercise of stock options	122	$ 1	121
Net income	277			277
Ending balance (shares) at Oct. 31, 2021		13,496,144
Ending balance at Oct. 31, 2021	$ 8,071	$ 14	$ 80,482	$ (72,425)