Exhibit 4.8

Second Amended and Restated Revolving Credit Note

        FOR VALUE RECEIVED, the undersigned, Selas Corporation of America, a Pennsylvania business corporation with its chief executive office and principal place of business at c/o RTI, 1260 Red Fox Road, Arden Hills, MN 55112 (the “Borrower”), promises to pay to the order of Wachovia Bank, National Association (formerly known as First Union National Bank) with offices located at Broad and Walnut Streets, Philadelphia, PA 19109 (the “Lender”) the principal sum of Four Million Five Hundred Thousand Dollars ($4,500,000) or, if less, the aggregate outstanding principal balance of all advances made by the Lender to the Borrower under the Amendment to Amended, Restated and Consolidated Loan Agreement dated of even date by and among the Borrower, Resistance Technology, Inc., a Minnesota business corporation with offices located at 1260 Red Fox Road, Arden Hills, MN 55112, RTI Electronics, Inc., a Delaware corporation with offices located at 1800 Via Burton Street, Anaheim, CA 92806 and Lender (as amended, restated, modified or supplemented from time to time, the “Agreement”), pursuant to the “Revolving Loan” as defined in the Agreement, together with interest, from the date of the Agreement, in like money, at said office of the Lender, at the time and at rates per annum as provided in the Agreement.

        This note (the “Note”) amends and completely restates and evidences the indebtedness outstanding under and is substituted for, but not in payment, satisfaction, cancellation or novation of, the Amended and Restated Revolving Credit Note dated March 18, 2004 which was issued by the Borrower to the Lender. As of the date hereof, this Note shall be deemed to be the Revolving Credit Facility Note referred to in the Agreement and shall evidence the indebtedness incurred under, and be entitled to the benefits of, the Agreement. All terms used and not otherwise defined in this Note shall have the meanings given to them in the Agreement. Upon the occurrence of any Event of Default set forth in the Agreement, the entire unpaid balance of principal and accrued interest of this Note and all other amounts due under the Agreement shall, at the option of the Lender, be immediately due and payable without presentment, demand, protest or notice of any kind, all of which are expressly waived.

        Until maturity (whether by acceleration or otherwise), the outstanding principal balance hereunder shall bear interest at the rates and shall be payable at the times and in the manner set forth in the Agreement. Subsequent to maturity, including after judgment, or upon the occurrence of any Event of Default set forth in the Agreement, interest on the outstanding principal balance hereunder shall accrue at an annual rate equal to the Base Rate plus five percent (5%) and shall be payable on demand.

        Time is of the e