Business Segments - Product Category (Details) - USD ($)	3 Months Ended		9 Months Ended
	Dec. 30, 2018	Dec. 24, 2017	Dec. 30, 2018	Dec. 24, 2017
Revenue and Gross Profit from External Customers
Revenues	$ 152,294,500	$ 146,260,300	$ 461,850,000	$ 431,354,600
Gross Profit	30,998,700	29,599,800	93,091,500	88,689,700
Base station infrastructure
Revenue and Gross Profit from External Customers
Revenues	67,988,000	57,282,000	217,817,000	175,800,000
Gross Profit	14,822,000	13,280,000	46,072,000	41,423,000
Network systems
Revenue and Gross Profit from External Customers
Revenues	21,477,000	24,024,000	66,818,000	77,041,000
Gross Profit	3,453,000	3,420,000	10,677,000	11,170,000
Installation, test and maintenance
Revenue and Gross Profit from External Customers
Revenues	8,306,000	9,255,000	24,628,000	23,927,000
Gross Profit	1,623,000	1,759,000	4,899,000	4,611,000
Mobile device accessories
Revenue and Gross Profit from External Customers
Revenues	54,524,000	55,699,000	152,587,000	154,587,000
Gross Profit	$ 11,101,000	$ 11,141,000	$ 31,444,000	$ 31,486,000