Segment Information (Details)
3 Months Ended 6 Months Ended
Feb. 23, 2016
operating_segment
Jan. 31, 2016
USD ($)
operating_segment
Jan. 31, 2015
USD ($)
Jan. 31, 2016
USD ($)
operating_segment
Jan. 31, 2015
USD ($)
Jul. 31, 2015
USD ($)
Segment Reporting Information [Line Items]            
Number of reportable operating segments | operating_segment   3   3    
Net sales   $ 70,323,000 $ 81,802,000 $ 134,440,000 $ 158,193,000  
Operating income (loss)   3,189,000 10,623,000 5,357,000 18,842,000  
Interest income and other (expense)   110,000 90,000 222,000 174,000  
Interest expense (income)   73,000 69,000 148,000 334,000  
Depreciation and amortization   3,736,000 4,243,000 7,693,000 8,749,000  
Expenditure for long-lived assets, including intangibles   827,000 1,398,000 1,463,000 2,145,000  
Total assets   462,170,000 471,487,000 462,170,000 471,487,000 $ 473,877,000
Amortization of stock-based compensation   1,074,000 1,061,000 2,125,000 2,398,000  
Transaction costs, acquisition of TCS   2,337,000 0 3,729,000 0  
Telecommunications Transmission Segment            
Segment Reporting Information [Line Items]            
Net sales   38,544,000 53,867,000 73,793,000 105,223,000  
Operating income (loss)   4,803,000 11,049,000 7,164,000 19,215,000  
Interest income and other (expense)   (15,000) (26,000) (32,000) (55,000)  
Interest expense (income)   73,000 69,000 148,000 136,000  
Depreciation and amortization   1,715,000 2,196,000 3,658,000 4,409,000  
Expenditure for long-lived assets, including intangibles   777,000 742,000 1,247,000 1,280,000  
Total assets   212,211,000 240,413,000 212,211,000 240,413,000  
RF Microwave Amplifiers Segment            
Segment Reporting Information [Line Items]            
Net sales   24,933,000 21,646,000 47,587,000 40,410,000  
Operating income (loss)   1,382,000 969,000 3,350,000 2,032,000  
Interest income and other (expense)   (7,000) (7,000) (7,000) (25,000)  
Interest expense (income)   0 0 0 0  
Depreciation and amortization   860,000 906,000 1,734,000 1,785,000  
Expenditure for long-lived assets, including intangibles   29,000 582,000 171,000 674,000  
Total assets   87,070,000 92,918,000 87,070,000 92,918,000  
Mobile Data Communication Segment            
Segment Reporting Information [Line Items]            
Net sales   6,846,000 6,289,000 13,060,000 12,560,000  
Operating income (loss)   3,735,000 2,709,000 6,734,000 5,576,000  
Interest income and other (expense)   2,000 3,000 5,000 6,000  
Interest expense (income)   0 0 0 0  
Depreciation and amortization   79,000 72,000 160,000 142,000  
Expenditure for long-lived assets, including intangibles   8,000 60,000 30,000 144,000  
Total assets   6,415,000 6,002,000 6,415,000 6,002,000  
Unallocated            
Segment Reporting Information [Line Items]            
Net sales   0 0 0 0  
Operating income (loss)   (6,731,000) (4,104,000) (11,891,000) (7,981,000)  
Interest income and other (expense)   130,000 120,000 256,000 248,000  
Interest expense (income)   0 0 0 198,000  
Depreciation and amortization   1,082,000 1,069,000 2,141,000 2,413,000  
Expenditure for long-lived assets, including intangibles   13,000 14,000 15,000 47,000  
Total assets   156,474,000 132,154,000 156,474,000 132,154,000  
Amortization of stock-based compensation   1,074,000 1,061,000 2,125,000 2,398,000  
Transaction costs, acquisition of TCS   2,337,000   3,729,000    
Expenses related to strategic alternatives analysis     0   585,000  
Telecommunications Transmission Sales to RF Microwave Amplifiers            
Segment Reporting Information [Line Items]            
Intersegment sales   652,000 720,000 1,305,000 1,009,000  
Telecommunications Transmissions Sales to Mobile Data Communications            
Segment Reporting Information [Line Items]            
Intersegment sales   87,000 141,000 108,000 337,000  
Rf Microwave Amplifiers Sales To Telecommunications Transmission            
Segment Reporting Information [Line Items]            
Intersegment sales   $ 13,000 0 $ 32,000 0  
Committed Secured Revolving Credit Facility            
Segment Reporting Information [Line Items]            
Line of Credit Facility, maximum borrowing capacity     $ 100,000,000   $ 100,000,000  
Subsequent Event            
Segment Reporting Information [Line Items]            
Number of reportable operating segments | operating_segment 2