Business Segments - Product Category (Details) - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 24, 2017	Sep. 30, 2018	Sep. 24, 2017
Revenue and Gross Profit from External Customers
Revenues	$ 158,636,100	$ 145,083,500	$ 309,555,500	$ 285,094,300
Gross Profit	31,394,700	29,923,100	62,092,800	59,089,900
Base station infrastructure
Revenue and Gross Profit from External Customers
Revenues	75,515,000	59,448,000	149,829,000	118,518,000
Gross Profit	15,534,000	14,086,000	31,250,000	28,143,000
Network systems
Revenue and Gross Profit from External Customers
Revenues	22,564,000	29,180,000	45,341,000	53,017,000
Gross Profit	3,561,000	3,921,000	7,224,000	7,750,000
Installation, test and maintenance
Revenue and Gross Profit from External Customers
Revenues	8,891,000	7,679,000	16,322,000	14,671,000
Gross Profit	1,803,000	1,433,000	3,276,000	2,852,000
Mobile device accessories
Revenue and Gross Profit from External Customers
Revenues	51,666,000	48,777,000	98,063,000	98,888,000
Gross Profit	$ 10,497,000	$ 10,483,000	$ 20,343,000	$ 20,345,000