Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Oct. 31, 2021	Oct. 31, 2020
Cash flows from operating activities:
Net (loss) income	$ (1,078)	$ 67
Non-cash charges to earnings	1,765	2,580
Net changes in operating assets and liabilities	974	(667)
Net cash provided by operating activities	1,661	1,980
Cash flows from investing activities:
Proceeds on redemption of marketable securities	1,427	1,521
Purchase of marketable securities	(1,164)	(909)
Purchase of property, plant, and equipment, and other assets	(1,108)	(781)
Net cash used in investing activities	(845)	(169)
Net cash used in financing activities:
Repayment of PPP Loan	0	(4,965)
Proceeds from UBS line of credit	0	3,000
Net cash used in financing activities	0	(1,965)
Net increase (decrease) in cash and cash equivalents	816	(154)
Cash and cash equivalents at beginning of period	9,807	3,808
Cash and cash equivalents at end of period	10,623	3,654
Supplemental disclosures of cash flow information:
Interest	40	46
Income Taxes	15	0
Income Taxes	$ 0	$ 477