Supplementary Financial Information - Inventories , Property and Equipment (Details) - USD ($)	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Inventories
Materials and supplies	$ 1,745,000	$ 887,000
Work in process	232,000	298,000
Finished goods	944,000	1,065,000
Total inventories	2,921,000	2,250,000
Property and Equipment, net
Accumulated depreciation	(6,600,000)	(7,508,000)
Net	2,333,000	2,064,000
Depreciation expense	819,000	729,000	$ 649,000
Equipment
Property and Equipment, net
Gross	6,053,000	7,078,000
Leasehold improvements
Property and Equipment, net
Gross	2,880,000	2,494,000
Cost of revenues
Property and Equipment, net
Depreciation expense	288,000	269,000	252,000
Operating expenses
Property and Equipment, net
Depreciation expense	$ 531,000	$ 397,000	$ 300,000