Business Segments - Segment Activity (Details)	3 Months Ended
Jul. 01, 2018 USD ($) segment product	Jun. 25, 2017 USD ($)
Business Segments
Number of reportable segment \| segment	2
Number of product categories \| product	4
Market unit activity
Revenues	$ 150,919,000
Gross Profit	30,698,100	$ 29,166,800
Directly allocable expenses	17,246,000	15,678,000
Income before provision for income taxes	1,562,400	1,216,700
Calculated under Revenue Guidance in Effect before Topic 606
Market unit activity
Revenues		140,011,000
Segments
Market unit activity
Directly allocable expenses	11,890,000	12,272,000
Income before provision for income taxes	18,808,000	16,895,000
Public Carrier
Market unit activity
Revenues	40,360,000
Gross Profit	5,626,000	4,128,000
Public Carrier \| Calculated under Revenue Guidance in Effect before Topic 606
Market unit activity
Revenues		26,598,000
Government
Market unit activity
Revenues	9,231,000
Gross Profit	2,137,000	2,004,000
Government \| Calculated under Revenue Guidance in Effect before Topic 606
Market unit activity
Revenues		8,445,000
Private System Operators
Market unit activity
Revenues	21,634,000
Gross Profit	4,865,000	4,607,000
Private System Operators \| Calculated under Revenue Guidance in Effect before Topic 606
Market unit activity
Revenues		21,042,000
Value-Added Resellers
Market unit activity
Revenues	34,682,000
Gross Profit	8,915,000	8,961,000
Value-Added Resellers \| Calculated under Revenue Guidance in Effect before Topic 606
Market unit activity
Revenues		35,040,000
Retail
Market unit activity
Revenues	45,012,000
Gross Profit	9,155,000	9,467,000
Retail \| Calculated under Revenue Guidance in Effect before Topic 606
Market unit activity
Revenues		48,886,000
Commercial Segment
Market unit activity
Revenues	105,907,000
Gross Profit	21,543,000	19,700,000
Commercial Segment \| Calculated under Revenue Guidance in Effect before Topic 606
Market unit activity
Revenues		91,125,000
Commercial Segment \| Segments
Market unit activity
Directly allocable expenses	8,081,000	8,522,000
Income before provision for income taxes	13,462,000	11,178,000
Commercial Segment \| Public Carrier
Market unit activity
Revenues	40,360,000
Gross Profit	5,626,000	4,128,000
Commercial Segment \| Public Carrier \| Calculated under Revenue Guidance in Effect before Topic 606
Market unit activity
Revenues		26,598,000
Commercial Segment \| Government
Market unit activity
Revenues	9,231,000
Gross Profit	2,137,000	2,004,000
Commercial Segment \| Government \| Calculated under Revenue Guidance in Effect before Topic 606
Market unit activity
Revenues		8,445,000
Commercial Segment \| Private System Operators
Market unit activity
Revenues	21,634,000
Gross Profit	4,865,000	4,607,000
Commercial Segment \| Private System Operators \| Calculated under Revenue Guidance in Effect before Topic 606
Market unit activity
Revenues		21,042,000
Commercial Segment \| Value-Added Resellers
Market unit activity
Revenues	34,682,000
Gross Profit	8,915,000	8,961,000
Commercial Segment \| Value-Added Resellers \| Calculated under Revenue Guidance in Effect before Topic 606
Market unit activity
Revenues		35,040,000
Retail Segment
Market unit activity
Revenues	45,012,000
Gross Profit	9,155,000	9,467,000
Retail Segment \| Calculated under Revenue Guidance in Effect before Topic 606
Market unit activity
Revenues		48,886,000
Retail Segment \| Segments
Market unit activity
Directly allocable expenses	3,809,000	3,750,000
Income before provision for income taxes	5,346,000	5,717,000
Retail Segment \| Retail
Market unit activity
Revenues	45,012,000
Gross Profit	$ 9,155,000	9,467,000
Retail Segment \| Retail \| Calculated under Revenue Guidance in Effect before Topic 606
Market unit activity
Revenues		$ 48,886,000

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The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Also includes the net amount of nonoperating interest (income) expense.

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- Definition

Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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