Business Segments - Product Category (Details) - USD ($)	3 Months Ended
	Jul. 01, 2018	Jun. 25, 2017
Revenue and Gross Profit from External Customers
Revenues	$ 150,919,000
Gross Profit	30,698,100	$ 29,166,800
Calculated under Revenue Guidance in Effect before Topic 606
Revenue and Gross Profit from External Customers
Revenues		140,011,000
Base station infrastructure
Revenue and Gross Profit from External Customers
Revenues	74,314,000
Gross Profit	15,716,000	14,057,000
Base station infrastructure | Calculated under Revenue Guidance in Effect before Topic 606
Revenue and Gross Profit from External Customers
Revenues		59,070,000
Network systems
Revenue and Gross Profit from External Customers
Revenues	22,777,000
Gross Profit	3,663,000	3,829,000
Network systems | Calculated under Revenue Guidance in Effect before Topic 606
Revenue and Gross Profit from External Customers
Revenues		23,837,000
Installation, test and maintenance
Revenue and Gross Profit from External Customers
Revenues	7,431,000
Gross Profit	1,473,000	1,419,000
Installation, test and maintenance | Calculated under Revenue Guidance in Effect before Topic 606
Revenue and Gross Profit from External Customers
Revenues		6,993,000
Mobile device accessories
Revenue and Gross Profit from External Customers
Revenues	46,397,000
Gross Profit	$ 9,846,000	9,862,000
Mobile device accessories | Calculated under Revenue Guidance in Effect before Topic 606
Revenue and Gross Profit from External Customers
Revenues		$ 50,111,000