7. Property, Plant and Equipment and Leases (Details)		12 Months Ended
	Jul. 25, 2018	Apr. 30, 2019 USD ($)	Apr. 30, 2018 USD ($) ft²	Feb. 01, 2018 ft²	Oct. 01, 2017
7. Property, Plant and Equipment and Leases (Details) [Line Items]
Depreciation		$ 2,802,000	$ 2,484,000
Cost of Property Repairs and Maintenance		309,000	466,000
Lessee, Operating Lease, Description	the Company signed an amendment to the lease which extends the current lease terms ten years and eight months through September 30, 2029
Operating Leases, Future Minimum Payments Due		13,593,000
Operating Leases, Rent Expense		1,200,000	1,700,000
Deferred Rent Credit, Noncurrent		236,000	$ 110,000
Long Island, NY Headquarters [Member]
7. Property, Plant and Equipment and Leases (Details) [Line Items]
Operating Leases, Rent Expense, Minimum Rentals		1,046,810
FEI-Elcom Office and Manufacturing Lease [Member]
7. Property, Plant and Equipment and Leases (Details) [Line Items]
Operating Leases, Rent Expense, Minimum Rentals		9,673
Area of Real Estate Property (in Square Feet) | ft²				9,000
FEI-Zyfer Office and Manufacturing Leases [Member]
7. Property, Plant and Equipment and Leases (Details) [Line Items]
Area of Real Estate Property (in Square Feet) | ft²			27,850
Lessee, Operating Lease, Renewal Term					88 months
Operating Leases, Future Minimum Payments Due			$ 312,000
Annual Rent Increase in 2029 [Member] | Long Island, NY Headquarters [Member]
7. Property, Plant and Equipment and Leases (Details) [Line Items]
Operating Leases, Rent Expense, Minimum Rentals		$ 1,276,056