Segment Information (Details)	3 Months Ended
	Oct. 31, 2015 USD ($) operating_segment	Oct. 31, 2014 USD ($) operating_segment	Jul. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of reportable operating segments | operating_segment	3	3
Net sales	$ 64,117,000	$ 76,391,000
Operating income (loss)	2,168,000	8,219,000
Interest income and other (expense)	112,000	84,000
Interest expense (income)	75,000	265,000
Depreciation and amortization	3,957,000	4,506,000
Expenditure for long-lived assets, including intangibles	636,000	747,000
Total assets	459,042,000	469,239,000	$ 473,877,000
Amortization of stock-based compensation	1,051,000	1,337,000
Telecommunications Transmission Segment
Segment Reporting Information [Line Items]
Net sales	35,249,000	51,356,000
Operating income (loss)	2,361,000	8,166,000
Interest income and other (expense)	(17,000)	(29,000)
Interest expense (income)	75,000	67,000
Depreciation and amortization	1,943,000	2,213,000
Expenditure for long-lived assets, including intangibles	470,000	538,000
Total assets	223,949,000	239,365,000
RF Microwave Amplifiers Segment
Segment Reporting Information [Line Items]
Net sales	22,654,000	18,764,000
Operating income (loss)	1,968,000	1,063,000
Interest income and other (expense)	0	(18,000)
Interest expense (income)	0	0
Depreciation and amortization	874,000	879,000
Expenditure for long-lived assets, including intangibles	142,000	92,000
Total assets	87,086,000	87,467,000
Mobile Data Communication Segment
Segment Reporting Information [Line Items]
Net sales	6,214,000	6,271,000
Operating income (loss)	2,999,000	2,867,000
Interest income and other (expense)	3,000	3,000
Interest expense (income)	0	0
Depreciation and amortization	81,000	70,000
Expenditure for long-lived assets, including intangibles	22,000	84,000
Total assets	4,859,000	4,898,000
Unallocated
Segment Reporting Information [Line Items]
Net sales	0	0
Operating income (loss)	(5,160,000)	(3,877,000)
Interest income and other (expense)	126,000	128,000
Interest expense (income)	0	198,000
Depreciation and amortization	1,059,000	1,344,000
Expenditure for long-lived assets, including intangibles	2,000	33,000
Total assets	143,148,000	137,509,000
Amortization of stock-based compensation	1,051,000	1,337,000
Acquisition plan expenses	1,392,000
Expenses related to strategic alternatives analysis		585,000
Telecommunications Transmission Sales to RF Microwave Amplifiers
Segment Reporting Information [Line Items]
Intersegment sales	653,000	289,000
Telecommunications Transmissions Sales to Mobile Data Communications
Segment Reporting Information [Line Items]
Intersegment sales	21,000	196,000
Rf Microwave Amplifiers Sales To Telecommunications Transmission
Segment Reporting Information [Line Items]
Intersegment sales	$ 19,000	0
Committed Secured Revolving Credit Facility [Member]
Segment Reporting Information [Line Items]
Line of Credit Facility, maximum borrowing capacity		$ 100,000,000