Document and Entity Information [Abstract] Statement, Equity Components [Axis] Equity Component [Domain] ASSETS Assets [Abstract] Current assets: Assets, Current [Abstract] Cash and cash equivalents, including restricted cash of $5,827 on October 31, 2011 and $5,821 on April 30, 2011 Cash and Cash Equivalents, at Carrying Value Restricted cash Restricted Cash and Cash Equivalents, Current Accounts receivable, net of allowance for doubtful accounts of $1,464 on October 31, 2011 and $2,147 on April 30, 2011 Accounts Receivable, Net, Current Allowance for doubtful accounts receivable Allowance for Doubtful Accounts Receivable, Current Inventories Inventory, Net Other current assets Other Assets, Current Deferred income taxes Deferred Tax Assets, Net, Current Income tax receivable Income Taxes Receivable, Current Total current assets Assets, Current, Total Total current assets Property, plant and equipment, net Property, Plant and Equipment, Net Intangibles, net Intangible Assets, Net (Excluding Goodwill) Other assets Other Assets, Noncurrent Total current assets Assets Total assets LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities and Equity [Abstract] Current liabilities: Liabilities, Current [Abstract] Accounts payable Accounts Payable, Current Accrued expenses Other Accrued Liabilities, Current Accrued payroll Other Employee Related Liabilities, Current Accrued taxes other than income Accrual for Taxes Other than Income Taxes, Current Accrued profit sharing Deferred Compensation Cash-based Arrangements, Liability, Current Accrued product/municipal liability Estimated Litigation Liability, Current Accrued warranty Product Warranty Accrual, Current Current portion of notes payable Notes Payable, Current Total current liabilities Liabilities, Current, Total Total current liabilities Deferred income taxes Deferred Tax Liabilities, Noncurrent Notes payable, net of current portion Notes Payable, Noncurrent Other non-current liabilities Other Liabilities, Noncurrent Total liabilities Liabilities, Total Total liabilities Commitments and contingencies (Note 16) Commitments and Contingencies Stockholders' equity: Stockholders' Equity Attributable to Parent [Abstract] Preferred stock, $.001 par value, 20,000,000 shares authorized, no shares issued or outstanding Preferred Stock, Value, Issued Preferred stock, par value Preferred Stock, Par or Stated Value Per Share Preferred stock, shares authorized Preferred Stock, Shares Authorized Preferred stock, shares issued Preferred Stock, Shares Issued Preferred stock, shares outstanding Preferred Stock, Shares Outstanding Common stock, $.001 par value, 100,000,000 shares authorized, 66,069,449 shares issued and 64,869,449 shares outstanding on October 31, 2011 and 65,710,531 shares issued and 64,510,531 shares outstanding on April 30, 2011 Common Stock, Value, Issued Common stock, par value Common Stock, Par or Stated Value Per Share Common stock, shares authorized Common Stock, Shares Authorized Common stock, shares issued Common Stock, Shares, Issued Common stock, shares outstanding Common Stock, Shares, Outstanding Additional paid-in capital Additional Paid in Capital, Common Stock Accumulated deficit Retained Earnings (Accumulated Deficit) Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Treasury stock, at cost (1,200,000 common shares) Treasury Stock, Value Treasury stock, at cost (1,200,000 common shares) Treasury stock, shares Treasury Stock, Shares Stockholders' Equity Attributable to Parent, Total Ending balance Beginning balance Total stockholders' equity Total stockholders' equity Total stockholders' equity Liabilities and Equity Total liabilities and stockholders' equity Net sales Revenue, Net Cost of sales Cost of Goods and Services Sold Gross profit Gross Profit Gross profit Operating expenses: Operating Expenses [Abstract] Research and development Research and Development Expense Selling and marketing Selling and Marketing Expense General and administrative General and Administrative Expense Total operating expenses Operating Expenses, Total Total operating expenses Operating income from continuing operations Operating Income (Loss) Operating income from continuing operations Other income/(expense): Nonoperating Income (Expense) [Abstract] Other income, net Other Nonoperating Income (Expense) Interest income Investment Income, Interest Interest expense Interest Expense Interest expense Total other income/(expense), net Nonoperating Income (Expense), Total Total other income/(expense), net Income from continuing operations before income taxes Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest Income from continuing operations before income taxes Income tax expense Income Tax Expense (Benefit) Income from continuing operations Income (Loss) from Continuing Operations Attributable to Parent Income from continuing operations Discontinued operations (Note 3): Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent [Abstract] Loss from operations of discontinued security solutions division Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax Income tax benefit Discontinued Operation, Tax Effect of Discontinued Operation Loss on discontinued operations Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent Loss on discontinued operations Net loss/comprehensive loss Net Income (Loss) Attributable to Parent Net loss/comprehensive loss Net income/(loss) per share (Note 14): Earnings Per Share [Abstract] Basic - continuing operations Income (Loss) from Continuing Operations, Per Basic Share Basic - discontinued operations Income (Loss) from Discontinued Operations, Net of Tax, Per Basic Share Diluted - continuing operations Income (Loss) from Continuing Operations, Per Diluted Share Diluted - discontinued operations Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share Weighted average number of common shares outstanding (Note 14): Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic Weighted Average Number of Shares Outstanding, Basic Diluted Weighted Average Number of Shares Outstanding, Diluted Statement [Table] Statement [Line Items] Common Stock Balance Ending balance, shares Beginning balance, shares Additional Paid-In Capital Accumulated Deficit Accumulated Other Comprehensive Income Treasury Stock Exercise of employee stock options, shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Exercise of employee stock options Stock Issued During Period, Value, Stock Options Exercised Stock-based compensation Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Book deduction of stock-based compensation in excess of tax deductions Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net Shares issued under employee stock purchase plan, shares Stock Issued During Period, Shares, Employee Stock Purchase Plans Shares issued under employee stock purchase plan Stock Issued During Period, Value, Employee Stock Purchase Plan Net loss Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net loss to net cash (used in)/provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Amortization and depreciation Depreciation, Depletion and Amortization Loss on sale of assets Gain (Loss) on Disposition of Assets Loss on sale of assets (Recoveries of)/provision for losses on accounts receivable Provision for Doubtful Accounts Impairment of long-lived assets Impairment of Long-Lived Assets Held-for-use Deferred income taxes Deferred Income Tax Expense (Benefit) Stock-based compensation expense Share-based Compensation Change in Contingent Consideration Change in contingent consideration Change in contingent consideration Change in contingent consideration Excess book deduction of stock-based compensation Excess Tax Benefit from Share-based Compensation, Operating Activities Excess book deduction of stock-based compensation Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable Increase (Decrease) in Accounts Receivable Accounts receivable Inventories Increase (Decrease) in Inventories Inventories Other current assets Increase (Decrease) in Other Current Assets Other current assets Income tax receivable/payable Increase (Decrease) in Income Taxes Payable, Net of Income Taxes Receivable Accounts payable Increase (Decrease) in Accounts Payable Accrued payroll Increase (Decrease) in Accrued Salaries Accrued taxes other than income Increase (Decrease) in Property and Other Taxes Payable Accrued profit sharing Increase (Decrease) in Deferred Compensation Accrued other expenses Increase (Decrease) in Other Accrued Liabilities Increase Decrease in Estimated Litigation Liability Accrued product/municipal liability Accrued product/municipal liability Accrued warranty Product Warranty Accrual, Period Increase (Decrease) Other assets Increase (Decrease) in Other Noncurrent Assets Other assets Other non-current liabilities Increase (Decrease) in Other Noncurrent Liabilities Net cash (used in)/provided by operating activities Net Cash Provided by (Used in) Operating Activities Net cash (used in)/provided by operating activities Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Payments to acquire patents and software Payments to Acquire Intangible Assets Payments to acquire patents and software Proceeds from sale of property and equipment Proceeds from Sale of Property, Plant, and Equipment Payments to acquire property and equipment Payments to Acquire Property, Plant, and Equipment Payments to acquire property and equipment Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Net cash used in investing activities Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Proceeds from loans and notes payable Proceeds from Issuance of Long-term Debt Cash paid for debt issue costs Payments of Debt Issuance Costs Cash paid for debt issue costs Proceeds from Energy Efficiency Incentive Programs Proceeds from energy efficiency incentive programs Proceeds from energy efficiency incentive programs Proceeds from exercise of options to acquire common stock including employee stock purchase plan Proceeds from Stock Options Exercised Taxes paid related to restricted stock issuance Payments Related to Tax Withholding for Share-based Compensation Taxes paid related to restricted stock issuance Payments on loans and notes payable Repayments of Long-term Debt Payments on loans and notes payable Net cash (used in)/provided by financing activities Net Cash Provided by (Used in) Financing Activities Net cash (used in)/provided by financing activities Net (decrease)/increase in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Net (decrease)/increase in cash and cash equivalents Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Supplemental disclosure of cash flow information Supplemental Cash Flow Information [Abstract] Cash paid for: Cash Paid Abstract Cash paid for: Interest Interest Paid Income taxes Income Taxes Paid Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Organization And Basis of Presentation [Abstract] Organization And Basis of Presentation [Abstract] Organization Nature of Operations [Text Block] Discontinued Operations Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] Discontinued Operations [Abstract] Discontinued Operations: [Abstract] Significant Accounting Policies Significant Accounting Policies [Text Block] Significant Accounting Policies [Abstract] Significant Accounting Policies [Abstract] Notes Payable Debt Disclosure [Text Block] Notes Payable [Abstract] Notes Payable [Abstract] Capital Lease Capital Leases in Financial Statements of Lessee Disclosure [Text Block] Capital Lease [Abstract] Capital Lease: [Abstract] Inventories Inventory Disclosure [Text Block] Inventories [Abstract] Inventories [Abstract] Intangible Assets Intangible Assets Disclosure [Text Block] Intangible Assets [Abstract] Intangible Assets [Abstract] Accrued Expenses Accounts Payable and Accrued Liabilities Disclosure [Text Block] Accrued Expenses [Abstract] Accrued Expenses [Abstract] Advertising Costs [Text Block] Advertising Costs Advertising Costs Advertising Costs [Abstract] Advertising Costs [Abstract] Warranty Reserve Product Warranty Disclosure [Text Block] Warranty Reserve [Abstract] Warranty Reserve [Abstract] Self Insurance Reserves [Text Block] Self-Insurance Reserves Self-Insurance Reserves Self-Insurance Reserves [Abstract] Self-Insurance Reserves [Abstract] Self-Insurance Reserves: Plant Consolidation [Text Block] Plant Consolidation Plant Consolidation Plant Consolidation [Abstract] Plant Consolidation [Abstract] Plant Consolidation: Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Stockholders' Equity [Abstract] Stockholders' Equity [Abstract] Income Taxes Income Tax Disclosure [Text Block] Income Taxes [Abstract] Income Taxes [Abstract] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Commitments and Contingencies [Abstract] Commitments and Contingencies [Abstract] Fair Value Measurements Fair Value, Measurement Inputs, Disclosure [Table Text Block] Fair Value Measurements [Abstract] Fair Value Measurements: [Abstract] Recent Accounting Pronouncements Description of New Accounting Pronouncements Not yet Adopted [Text Block] Recent Accounting Pronouncements [Abstract] Recent Accounting Pronouncements: [Abstract] Amendment Flag Current Fiscal Year End Date Document Period End Date Document Type Entity Central Index Key Entity Common Stock, Shares Outstanding Entity Current Reporting Status Entity Filer Category Entity Registrant Name Entity Voluntary Filers Entity Well-known Seasoned Issuer Entity Public Float Document Fiscal Period Focus Document Fiscal Year Focus Consolidated Balance Sheets [Abstract] Consolidated Statements of Operations and Comprehensive Loss [Abstract] Consolidated Statement of Changes in Stockholders' Equity [Abstract] Consolidated Statements of Cash Flows [Abstract]