Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2021	Apr. 30, 2020
Income Statement [Abstract]
Revenues	$ 54,254	$ 41,507
Cost of revenues	37,333	35,759
Gross margin	16,921	5,748
Selling and administrative expenses	13,189	11,593
Research and development expenses	4,690	5,077
Operating loss	(958)	(10,922)
Other income (expense):
Investment income	458	329
Interest expense	(127)	(107)
Other income (expense), net	1,103	(1,068)
Income (loss) before benefit from income taxes	476	(11,768)
Benefit from income taxes	(204)	(1,742)
Net income (loss)	$ 680	$ (10,026)
Net income (loss) per common share:
Basic and diluted earnings (loss) per share (in Dollars per share)	$ 0.07	$ (1.10)
Weighted average shares outstanding:
Basic (in Shares)	9,177,537	9,073,609
Diluted (in Shares)	9,248,425	9,325,487
Consolidated Statements of Comprehensive Income (Loss)
Net income (loss)	$ 680	$ (10,026)
Unrealized (loss) gain on marketable securities:
Change in market value of marketable securities before reclassification, net of tax	(177)	443
Reclassification adjustment for realized gains included in net income, net of tax	(22)	1
Total unrealized (loss) gain on marketable securities, net of tax	(199)	444
Comprehensive income (loss)	$ 481	$ (9,582)