Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017
Cash flows from operating activities:
Net income	$ 25,041,000	$ 29,769,000	$ 15,827,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of property, plant and equipment	11,927,000	13,655,000	14,354,000
Amortization of intangible assets with finite lives	18,320,000	21,075,000	22,823,000
Amortization of stock-based compensation	11,427,000	8,569,000	8,506,000
Amortization of deferred financing costs	1,099,000	2,196,000	1,977,000
Estimated contract settlement costs	6,351,000	0	0
Settlement of intellectual property litigation	(3,204,000)	0	(12,020,000)
Write-off of deferred financing costs	3,217,000	0	0
Changes in other liabilities	(1,056,000)	0	0
Loss (gain) on disposal of property, plant and equipment	144,000	79,000	(126,000)
Provision for allowance for doubtful accounts	1,136,000	573,000	497,000
Provision for excess and obsolete inventory	6,015,000	5,628,000	2,900,000
Deferred income tax expense (benefit)	4,283,000	(6,379,000)	9,056,000
Excess income tax benefit from stock-based award exercises	0	0	(82,000)
Changes in assets and liabilities, net of effects of business acquisition:
Accounts receivable	6,315,000	(24,578,000)	25,508,000
Inventories	(3,787,000)	(20,065,000)	7,812,000
Prepaid expenses and other current assets	915,000	787,000	(956,000)
Other assets	102,000	(140,000)	666,000
Accounts payable	(21,290,000)	13,728,000	(4,472,000)
Accrued expenses and other current liabilities	3,554,000	(3,374,000)	(21,796,000)
Contract liabilities	(127,000)	9,143,000	(2,431,000)
Other liabilities, non-current	(84,000)	(682,000)	(1,442,000)
Interest payable	151,000	234,000	(1,039,000)
Income taxes payable	(2,418,000)	126,000	1,355,000
Net cash provided by operating activities	68,031,000	50,344,000	66,917,000
Cash flows from investing activities:
Payment for acquisition of Solacom Technologies Inc., net of cash acquired	(25,883,000)	0	0
Payment for acquisition of the GD NG-911 business	(10,000,000)	0	0
Purchases of property, plant and equipment	(8,785,000)	(8,642,000)	(8,150,000)
Net cash used in investing activities	(44,668,000)	(8,642,000)	(8,150,000)
Cash flows from financing activities:
Net borrowings of long-term debt under Credit Facility	165,000,000	0	0
Repayment of debt under Term Loan portion of Prior Credit Facility	(120,121,000)	(18,960,000)	(33,567,000)
Net payments under Revolving Loan portion of Prior Credit Facility	(48,603,000)	(8,800,000)	(26,500,000)
Cash dividends paid	(9,789,000)	(9,538,000)	(18,872,000)
Remittance of employees' statutory tax withholdings for stock awards	(5,042,000)	(1,143,000)	(262,000)
Repayment of principal amounts under capital lease and other obligations	(1,906,000)	(2,802,000)	(3,592,000)
Payment of deferred financing costs	(1,813,000)	0	(1,085,000)
Proceeds from issuance of employee stock purchase plan shares	935,000	855,000	694,000
Proceeds from exercises of stock options	216,000	326,000	0
Payment of shelf registration costs and equity issuance costs	(148,000)	0	(626,000)
Excess income tax benefit from stock-based award exercises	0	0	82,000
Net cash used in financing activities	(21,271,000)	(40,062,000)	(83,728,000)
Net increase (decrease) in cash and cash equivalents	2,092,000	1,640,000	(24,961,000)
Cash and cash equivalents at beginning of year	43,484,000	41,844,000	66,805,000
Cash and cash equivalents at end of year	45,576,000	43,484,000	41,844,000
Cash paid (received) during the year for:
Interest	7,669,000	7,291,000	10,424,000
Income taxes, net	2,005,000	1,112,000	(758,000)
Non-cash investing and financing activities:
Accrued remittance of employees' statutory tax withholdings for fully-vested share units	1,787,000	2,963,000	0
Cash dividends declared but unpaid (including accrual of dividend equivalents)	2,733,000	2,656,000	2,616,000
Capital lease and other obligations incurred	0	1,306,000	68,000
Accrued additions to property, plant and equipment	902,000	719,000	1,221,000
Issuance (forfeiture) of restricted stock	1,000	(1,000)	14,000
Common stock issued for acquisition of Solacom Technologies Inc.	$ 5,606,000	$ 0	$ 0