PROMISSORY NOTE

Exhibit 10.5

National City

PROMISSORY NOTE

PROMISE TO PAY. Sparton Corporation (“Borrower”) promises to pay National City Bank (“Lender”), or order, in lawful money of the United States of America, the principal amount of Twenty Million & 00/100 Dollars ($20,000,000.00) or so much as may be outstanding, together with interest on the unpaid outstanding principal balance of each advance. Interest shall be calculated from the date of each advance until repayment of each advance.

PAYMENT . Borrower will pay this loan in one payment of all outstanding principal plus all accrued unpaid interest on January 20, 2009. In addition, Borrower will pay regular monthly payments of all accrued unpaid interest due as of each payment date, beginning February 22, 2008, with all subsequent interest payments to be due on the same day of each month after that. Unless otherwise agreed or required by applicable law, payments will be applied first to any accrued unpaid interest; then to principal; then to any unpaid collection costs; and then to any late charges. The annual interest rate for this Note is computed on a 365/360 basis; that is, by applying the ratio of the annual interest rate over a year of 360 days, multiplied by the outstanding principal balance, multiplied by the actual number of days the principal balance is outstanding. Borrower will pay Lender at Lender’s address shown above or at such other place as Lender may designate in writing.

VALUABLE INTERST RATE. The interest rate on this Note is subject to change from time to time based on changes in an index which is the fluctuating rate per annum which is designated or published from time to time by Lender as being its “One Month Libor Rate”, it being acknowledged that the Index is not necessarily a) the lowest rate of interest or the only “LIBOR” denominated interest rate then available from Lender on fluctuating rate loans or b) calculated in the same manner as any other “LIBOR” denominated interest rate offered by Lender. It is further acknowledged that the Index is not necessarily calculated in the same manner as any other “LIBOR” denominated interest rate offered by any other bank or published by any publication (the “Index”). Lender will tell Borrower the current Index rate upon Borrower’s request. The interest rate change will not occur more often than each month on the Change Date. Borrower understands that Lender may make loans based on other rates as well. The interest rate to be applied to the unpaid principal balance during this Note will be at a rate of 1.250 percentage points over the Index. NOTICE: Under no circumstances will the interest rate on this Note be more than the maximum rate allowed by applicable law.

PREPAYMENT. Borrower may pay without penalty all or a portion of the amount owed earlier than it is due. Early payments will not, unless agreed to by Lender in writing, relieve Borrower of Borrower’s obligation to continue to make payments of accrued unpaid interest. Rather, early payments will reduce the principal balance due. Borrower agrees not to send Lender payments marked “paid in full”, “without recourse”, or similar language. If Borrower sends such a payment, Lender may accept it without losing any of Lender’s rights under this Note, and Borrower will remain obligated to pay any further amount owed to Lender. All written communications concerning disputed amounts, including any check or other payment instrument that indicates that the payment constitutes “payment in full” of the amount owed or that is tendered with other conditions or limitations or as full satisfaction of a disputed amount must be mailed or delivered to: National City Bank, Central Region, 120 North Washington Square, Lansing MI 48933.

LATE CHARGE. If a payment is 20 days or more late, Borrower will be charged 5.000% of the unpaid portion of regularly scheduled payment or $20.00, whichever is greater.

INTERST AFTER DEFAULT. Upon default, including failure to pay upon final maturity, the interest rate on this Note shall be increased by adding a 2.000 percentage point margin (“Default Rate Margin”). The Default Rate Margin shall also apply to each succeeding interest rate change that would have applied had there been no default. However, in no event will the interest rate exceed the maximum interest rate limitations under applicable law.

DEFAULT. Each of the following shall constitute an event of default (“Event of Default”) under this Note:

Payment Default. Borrower fails to make any payment when due under this Note.

Other Defaults. Borrower fails to comply with or to perform any other term, obligation, covenant or condition contained in this Note or in any of the related documents or to comply with or to perform any term, obligation, covenant or condition contained in any other agreement between Lender and Borrower.

False Statements. Any warranty, representation or statement made or furnished to Lender by Borrower or on Borrower’s behalf under this Note or the related documents is false or misleading in any material respect, either now or at the time made or furnished or becomes false or misleading at any time thereafter.

Insolvency. The dissolution or termination of Borrower’s existence as a going business, the insolvency of Borrower, the appointment of a receiver for any part of Borrower’s property, any assignment for the benefit of creditors, any type of creditor workout, or the commencement of any proceeding under any bankruptcy or insolvency laws by or against Borrower.

Creditor or Forfeiture Proceedings. Commencement of foreclosure or forfeiture proceedings, whether by judicial proceeding, self-help, repossession or any other method, by any creditor of Borrower or by an governmental agency against any collateral securing the loan. This includes a garnishment of any of Borrower’s accounts, including deposit accounts, with Lender. However, this Event of Default shall not apply if there is a good faith dispute by Borrower as to the validity or reasonableness of the claim which is the