Operating Segments - Product Category (Details)	3 Months Ended								12 Months Ended
	Mar. 29, 2020 USD ($)	Dec. 29, 2019 USD ($)	Sep. 29, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jul. 01, 2018 USD ($)	Mar. 29, 2020 USD ($) product	Mar. 31, 2019 USD ($)	Apr. 01, 2018 USD ($)
Revenue and Gross Profit from External Customers
Number of product categories | product									4
Revenues	$ 128,179,900	$ 139,578,200	$ 141,810,900	$ 130,729,300	$ 144,963,800	$ 152,294,500	$ 158,636,100	$ 150,919,400	$ 540,298,300	$ 606,813,800	$ 580,274,700
Gross Profit	$ 17,165,900	$ 23,074,300	$ 26,319,300	$ 25,263,500	$ 28,267,200	$ 30,998,700	$ 31,394,700	$ 30,698,100	91,823,000	121,358,700	120,228,400
Base station infrastructure
Revenue and Gross Profit from External Customers
Revenues									286,642,000	292,787,000	248,949,000
Gross Profit									59,033,000	61,458,000	58,015,000
Network systems
Revenue and Gross Profit from External Customers
Revenues									87,553,000	86,555,000	98,642,000
Gross Profit									13,742,000	13,604,000	14,649,000
Installation, test and maintenance
Revenue and Gross Profit from External Customers
Revenues									28,064,000	32,595,000	33,200,000
Gross Profit									5,092,000	6,433,000	6,266,000
Mobile device accessories
Revenue and Gross Profit from External Customers
Revenues									138,039,000	194,877,000	199,484,000
Gross Profit									$ 13,956,000	$ 39,864,000	$ 41,298,000