Intangible assets (Tables)

12 Months Ended

Mar. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible assets

	March 31,
	2018			2019
	$ in thousands			$ in thousands
Cost		6,348			5,951
Less: accumulated amortization		(3,561	)		(3,613	)
		2,787			2,338

Components of other intangible assets

	March 31,
	2018		2019
	$ in thousands		$ in thousands
Land use right of factory land in Shenzhen, Guangdong, PRC		1,274		1,014
Land use right of factory land in Xinxing, Guangdong, PRC		1,513		1,324
		2,787		2,338

Schedule of amortization expenses

Year ending March 31,		$ in thousands
	2020		275
	2021		275
	2022		275
	2023		275
	2024		275
	Thereafter		963
	Total		2,338