Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2022	Oct. 31, 2021	Oct. 31, 2022	Oct. 31, 2021
Income Statement [Abstract]
Revenues	$ 8,949	$ 12,936	$ 17,153	$ 25,890
Cost of revenues	8,599	8,845	16,808	17,738
Gross margin	350	4,091	345	8,152
Selling and administrative expenses	2,034	2,411	4,026	6,805
Research and development expenses	599	1,377	1,709	2,732
Operating (loss) income	(2,283)	303	(5,390)	(1,385)
Other income (expense):
Investment (expense) income	(12)	98	24	191
Interest expense	(18)	(20)	(63)	(40)
Other income (expense), net	0	118	0	158
(Loss) income before provision for income taxes	(2,313)	499	(5,429)	(1,076)
Provision for income taxes	1	2	2	2
Net (loss) income	$ (2,314)	$ 497	$ (5,431)	$ (1,078)
Net (loss) income per common share:
Basic and diluted (loss) income per share (in Dollars per share)	$ (0.25)	$ 0.05	$ (0.58)	$ (0.12)
Weighted average shares outstanding:
Basic (in Shares)	9,326,347	9,256,255	9,317,143	9,246,240
Diluted (in Shares)	9,326,347	9,301,528	9,317,143	9,246,240
Condensed Consolidated Statements of Comprehensive (Loss) Income
Net (loss) income	$ (2,314)	$ 497	$ (5,431)	$ (1,078)
Unrealized loss on marketable securities:
Change in market value of marketable securities before reclassification, net of tax	(581)	(157)	(552)	(72)
Reclassification adjustment for realized gains (losses) included in net income, net of tax	16	0	1	(6)
Total unrealized loss on marketable securities, net of tax	(565)	(157)	(551)	(78)
Comprehensive (loss) income	$ (2,879)	$ 340	$ (5,982)	$ (1,156)