Operating Segments - Segment Activity (Details)	3 Months Ended								12 Months Ended
	Mar. 28, 2021 USD ($)	Dec. 27, 2020 USD ($)	Sep. 27, 2020 USD ($)	Jun. 28, 2020 USD ($)	Mar. 29, 2020 USD ($)	Dec. 29, 2019 USD ($)	Sep. 29, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 28, 2021 USD ($) segment	Mar. 29, 2020 USD ($)	Mar. 31, 2019 USD ($)
Business Segment
Number of reportable segment | segment									1
Market unit activity
Revenues	$ 88,733,100	$ 99,237,600	$ 88,892,400	$ 96,477,600	$ 105,839,700	$ 100,844,000	$ 103,651,000	$ 98,679,700	$ 373,340,700	$ 409,014,400	$ 419,044,800
Gross Profit	$ 16,826,000	$ 17,315,700	$ 17,121,200	$ 16,452,700	$ 19,588,400	$ 19,647,700	$ 20,184,300	$ 20,221,500	67,715,600	79,641,900	84,404,700
Public carrier
Market unit activity
Revenues									149,825,000	156,395,000	156,983,000
Gross Profit									16,585,000	18,699,000	20,275,000
Value-added resellers and integrators
Market unit activity
Revenues									223,516,000	252,619,000	262,062,000
Gross Profit									$ 51,131,000	$ 60,943,000	$ 64,130,000