Operating Segments - Product Category (Details) - USD ($)	3 Months Ended								12 Months Ended
	Apr. 01, 2018	Dec. 24, 2017	Sep. 24, 2017	Jun. 25, 2017	Mar. 26, 2017	Dec. 25, 2016	Sep. 25, 2016	Jun. 26, 2016	Apr. 01, 2018	Mar. 26, 2017	Mar. 27, 2016
Revenue and Gross Profit from External Customers
Revenues	$ 148,920,100	$ 146,260,300	$ 145,083,500	$ 140,010,800	$ 122,602,900	$ 147,198,400	$ 134,633,800	$ 128,860,000	$ 580,274,700	$ 533,295,100	$ 530,682,100
Gross Profit	$ 31,538,700	$ 29,599,800	$ 29,923,100	$ 29,166,800	$ 25,937,600	$ 29,968,600	$ 28,755,600	$ 27,106,000	120,228,400	111,767,800	111,965,900
Base station infrastructure
Revenue and Gross Profit from External Customers
Revenues									248,949,000	209,869,000	206,604,000
Gross Profit									58,015,000	54,280,000	51,610,000
Network systems
Revenue and Gross Profit from External Customers
Revenues									98,642,000	87,222,000	83,480,000
Gross Profit									14,649,000	11,897,000	12,893,000
Installation, test and maintenance
Revenue and Gross Profit from External Customers
Revenues									33,200,000	31,851,000	34,936,000
Gross Profit									6,266,000	5,921,000	6,607,000
Mobile device accessories
Revenue and Gross Profit from External Customers
Revenues									199,484,000	204,353,000	205,662,000
Gross Profit									$ 41,298,000	$ 39,670,000	$ 40,856,000