Intangible Assets

6 Months Ended

Oct. 31, 2020

Intangible Assets Gross Excluding Goodwill [Abstract]

(5) Intangible Assets:

The following table presents a summary of intangible assets as of October 31, 2020 and April 30, 2020 (in thousands):

	October 31, 2020							April 30, 2020
	Gross							Gross
	Carrying		Accumulated			Net Carrying		Carrying		Accumulated			Net Carrying
	Amount		Amortization			Amount		Amount		Amortization			Amount
Customer relationships	$	2,580	$	(2,004	)	$	576	$	2,580	$	(1,932	)	$	648
Developed technology		200		(188	)		12		200		(176	)		24
Patents, trademarks, and trade names		8,210		(5,275	)		2,935		8,140		(5,091	)		3,049
		10,990		(7,467	)		3,523		10,920		(7,199	)		3,721
Patents in progress		935		—			935		654		—			654
Total definite-lived intangible assets	$	11,925	$	(7,467	)	$	4,458	$	11,574	$	(7,199	)	$	4,375

We amortize intangible assets with determinable lives over a weighted-average period of approximately five years. The weighted-average periods of amortization by intangible asset class is approximately five years for customer relationships; six years for developed technology; and five years for patents, trademarks, and trade names. Amortization expense, excluding amortization of deferred financing costs, amounted to $134,000 and $156,000 for the three months ended October 31, 2020 and 2019, respectively. Amortization expense, excluding amortization of deferred financing costs, amounted to $268,000 and $327,000 for the six months ended October 31, 2020 and 2019, respectively.

Estimated amortization expense of intangible assets for the remainder of fiscal 2021 and succeeding fiscal years is as follows (in thousands):

Fiscal	Amount
2021	$	268
2022		493
2023		452
2024		443
2025		432
Thereafter		1,435
Total	$	3,523