Segment Information (Details) (USD $)	3 Months Ended	9 Months Ended	12 Months Ended
Apr. 30, 2015 operating_segment	Apr. 30, 2014 operating_segment	Apr. 30, 2015 operating_segment	Apr. 30, 2014 operating_segment	Jul. 31, 2014 operating_segment
Segment Reporting Information [Line Items]
Number of reportable operating segments	3us-gaap_NumberOfOperatingSegments	3us-gaap_NumberOfOperatingSegments	3us-gaap_NumberOfOperatingSegments	3us-gaap_NumberOfOperatingSegments	3us-gaap_NumberOfOperatingSegments
Net sales	$ 71,633,000us-gaap_SalesRevenueNet	$ 88,905,000us-gaap_SalesRevenueNet	$ 229,826,000us-gaap_SalesRevenueNet	$ 257,772,000us-gaap_SalesRevenueNet
Operating income (loss)	7,160,000us-gaap_OperatingIncomeLoss	10,567,000us-gaap_OperatingIncomeLoss	26,002,000us-gaap_OperatingIncomeLoss	31,838,000us-gaap_OperatingIncomeLoss
Interest income and other (expense)	107,000us-gaap_InvestmentIncomeInterest	256,000us-gaap_InvestmentIncomeInterest	281,000us-gaap_InvestmentIncomeInterest	757,000us-gaap_InvestmentIncomeInterest
Interest expense (income)	72,000us-gaap_InterestExpense	1,993,000us-gaap_InterestExpense	406,000us-gaap_InterestExpense	6,009,000us-gaap_InterestExpense
Depreciation and amortization	4,471,000	4,280,000	13,220,000	12,843,000
Expenditure for long-lived assets, including intangibles	688,000	1,112,000	2,833,000	4,536,000
Total assets	473,795,000us-gaap_Assets	633,605,000us-gaap_Assets	473,795,000us-gaap_Assets	633,605,000us-gaap_Assets	473,852,000us-gaap_Assets
Amortization of stock-based compensation	1,244,000	1,070,000	3,642,000	3,086,000
Telecommunications Transmission Segment
Segment Reporting Information [Line Items]
Net sales	45,642,000	61,235,000	150,865,000	172,121,000
Operating income (loss)	7,283,000	10,353,000	26,498,000	29,550,000
Interest income and other (expense)	(6,000)	21,000	(61,000)	9,000
Interest expense (income)	72,000	62,000	208,000	182,000
Depreciation and amortization	2,198,000	2,193,000	6,607,000	6,683,000
Expenditure for long-lived assets, including intangibles	403,000	916,000	1,683,000	3,830,000
Total assets	237,811,000	251,156,000	237,811,000	251,156,000
RF Microwave Amplifiers Segment
Segment Reporting Information [Line Items]
Net sales	19,676,000	22,499,000	60,086,000	64,737,000
Operating income (loss)	1,254,000	1,445,000	3,286,000	3,113,000
Interest income and other (expense)	6,000	(14,000)	(19,000)	(32,000)
Interest expense (income)	0	0	0	0
Depreciation and amortization	940,000	939,000	2,725,000	2,827,000
Expenditure for long-lived assets, including intangibles	117,000	158,000	791,000	415,000
Total assets	95,217,000	89,177,000	95,217,000	89,177,000
Mobile Data Communications Segment
Segment Reporting Information [Line Items]
Net sales	6,315,000	5,171,000	18,875,000	20,914,000
Operating income (loss)	2,642,000	2,318,000	8,218,000	9,697,000
Interest income and other (expense)	4,000	3,000	10,000	9,000
Interest expense (income)	0	0	0	(3,000)
Depreciation and amortization	78,000	62,000	220,000	199,000
Expenditure for long-lived assets, including intangibles	149,000	38,000	293,000	284,000
Total assets	6,213,000	5,811,000	6,213,000	5,811,000
Unallocated
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Operating income (loss)	(4,019,000)	(3,549,000)	(12,000,000)	(10,522,000)
Interest income and other (expense)	103,000	246,000	351,000	771,000
Interest expense (income)	0	1,931,000	198,000	5,830,000
Depreciation and amortization	1,255,000	1,086,000	3,668,000	3,134,000
Expenditure for long-lived assets, including intangibles	19,000	0	66,000	7,000
Total assets	134,554,000	287,461,000	134,554,000	287,461,000
Amortization of stock-based compensation	1,244,000	1,070,000	3,642,000	3,086,000
Expenses related to strategic alternatives analysis	0	0	585,000	0
Telecommunications Transmission Sales to RF Microwave Amplifiers
Segment Reporting Information [Line Items]
Intersegment sales	824,000	521,000	1,833,000	1,286,000
Telecommunications Transmissions Sales to Mobile Data Communications
Segment Reporting Information [Line Items]
Intersegment sales	127,000	41,000	464,000	213,000
Rf Microwave Amplifiers Sales To Telecommunications Transmission
Segment Reporting Information [Line Items]
Intersegment sales	$ 0	$ 3,000	$ 0	$ 137,000

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