Exhibit 4(x)

THE DAYTON POWER AND LIGHT COMPANY

AND

THE BANK OF NEW YORK
(formerly Irving Trust Company)

Forty-Fifth Supplemental Indenture

Dated as of November 1, 2007

THE DAYTON POWER AND LIGHT COMPANY

FORTY-FIFTH SUPPLEMENTAL INDENTURE
DATED AS OF NOVEMBER 1, 2007

TABLE OF CONTENTS

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FORTY-FIFTH SUPPLEMENTAL INDENTURE, dated as of November 1, 2007, between THE DAYTON POWER AND LIGHT COMPANY, a corporation of the State of Ohio (hereinafter sometimes called the Company), party of the first part, and THE BANK OF NEW YORK (formerly Irving Trust Company), a corporation of the State of New York (hereinafter sometimes called the Trustee), as Trustee, party of the second part.

WHEREAS, the Company has heretofore executed and delivered to Irving Trust Company (now The Bank of New York) a certain Indenture, dated as of October 1, 1935 (hereinafter sometimes called the First Mortgage), to secure the payment of the principal of and interest on an issue of bonds of the Company, unlimited in aggregate principal amount (hereinafter sometimes called the Bonds); and

WHEREAS, the Company has issued under the First Mortgage its Bonds of a series known as the First and Refunding Mortgage Bonds, 3½% Series Due 1960, authorized in unlimited aggregate principal amount, all of which have been redeemed or otherwise retired; and

WHEREAS, in Article Two of the First Mortgage it is provided in substance, among other things, that the Bonds may be issued in series, the Bonds of each series maturing on such dates and bearing interest at such rates, respectively, as the Board of Directors of the Company may determine prior to the authentication thereof; and

WHEREAS, the Company has heretofore executed and delivered to the Trustee forty-four supplemental Indentures numbered, dated and, except as set forth below, providing for their respective series of First Mortgage Bonds, all as set forth in the tabulation below:

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WHEREAS, said Eleventh Supplemental Indenture, which created the 5 ⁵ / ₈ % Series Due 1997, provided in its Article Three for certain amendments to the First Mortgage, as theretofore amended, each such amendment to become effective on the earliest date on which either (a) there shall not be any Bonds outstanding of Series Due 1975, Series Due 1978, Series A, Due 1978, Series Due 1982, Series Due 1984, or Series Due 1993, or (b) there shall have been executed and delivered a supplemental indenture or indentures embodying said amendment (either alone or with other amendments) consented to by the holders of seventy-five per centum (75%) in aggregate principal amount of the Bonds at the time outstanding of the series enumerated in the foregoing clause (a), or of each said series of which Bonds are then outstanding; and

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WHEREAS, said Fifteenth Supplemental Indenture, which created the 8 ¹ / ₈ % Series Due 2001, provided (a) in its Article Four for an amendment to the First Mortgage, as theretofore amended, to become effective on the date on which the amendments provided for by Section 3 of Article Three of said Eleventh Supplemental Indenture shall become effective and (b) in its Article Five for certain additional amendments to the First Mortgage, as theretofore amended, to become effective on the earliest date on which either (i) there shall not be any Bonds outstanding of Series Due 1975, Series Due 1978, Series A, Due 1978, Series Due 1982, Series Due 1984, Series Due 1993, Series Due 1997, Series Due 1998, Series Due 1999, or Series Due 2000, or (ii) there shall have been executed and delivered a supplemental indenture or indentures embodying said amendments (either alone or with other amendments) consented to by the holders of seventy-five per centum (75%) in aggregate principal amount of the Bonds at the time outstanding of the series enumerated in the foregoing clause (i), or of each said series of which Bonds are then outstanding; and

WHEREAS, the Company has heretofore executed and delivered to the Trustee a Sixteenth Supplemental Indenture dated as of October 3, 1972, which provided in its Article One for an amendment of Article Five of the First Mortgage, as theretofore amended, altering the requirements for the opinion of counsel to be delivered to the Trustee as a condition precedent to the authentication and delivery of additional Bonds under Article Five or the withdrawal of cash under Article Seven of the First Mortgage, as theretofore amended; and

WHEREAS, none of the Bonds of Series Due 1975, Series Due 1978, Series A, Due 1978, Series Due 1982, Series Due 1984, or Series Due 1993 remain outstanding and the amendments contained in said Eleventh Supplemental Indenture have become effective; and

WHEREAS, none of the Bonds of Series Due 1975, Series Due 1978, Series A, Due 1978, Series Due 1982, Series Due 1984, Series Due 1993, Series Due 1997, Series Due 1998, Series Due 1999, or Series Due 2000 remain outstanding and the amendments contained in said Fifteenth Supplemental Indenture that did not theretofore become effective by virtue of the Sixteenth Supplemental Indenture have become effective; and

WHEREAS, said Forty-Second Supplemental Indenture, which created the 5 ¹ / ₈ % Series Due 2013, provided in its Article Two for certain amendments to the First Mortgage, as theretofore amended, to become effective on the earliest date on which either (i) there shall not be any Bonds outstanding of 6.35% Series Due 2007, Pollution Control Series 1992-A Due 2027, Pollution Control Series 1992-B Due 2027, Pollution Control Series 1992-C Due 2022, Series Due 2026 and Series Due 2024, or (ii) there shall have been executed and delivered a supplemental indenture or indentures embodying said amendment (either alone or with other amendments) consented to by the holders of seventy-five per centum (75%) in aggregate principal amount of the Bonds at the time outstanding of the series enumerated in the foregoing clause (i); and

WHEREAS, none of the Bonds of 6.35% Series Due 2007, Pollution Control Series 1992-A Due 2027, Pollution Control Series 1992-B Due 2027, Pollution Control Series 1992-C

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Due 2022, Series Due 2026 and Series Due 2024 remain outstanding and the amendments contained in said Forty-Second Supplemental Indenture have become effective; and

WHEREAS, the First Mortgage as amended by the First through the Forty-Fourth Supplemental Indentures is hereinafter called the First Mortgage as amended; and

WHEREAS, it is provided in Article Seven of the First Mortgage as amended, among other things, that the Company may issue additional Bonds thereunder upon the deposit with the Trustee of cash equal to the principal amount of such additional Bonds to be issued; it is provided in Article Six of the First Mortgage as amended, among other things, that if Bonds are paid, retired, redeemed, canceled or surrendered to the Trustee for cancellation (except when canceled pursuant to certain provisions of the First Mortgage as amended), the Company may issue additional Bonds thereunder in principal amount equivalent to the principal amount of the Bonds so paid, retired, redeemed, canceled or surrendered to the Trustee for cancellation; it is provided in Article Five of the First Mortgage as amended, among other things, that the Company may issue additional Bonds thereunder upon the basis of property additions in accordance with and subject to the conditions, provisions and limitations set forth in said Article Five; and it is provided in Article Eighteen of the First Mortgage as amended, among other things, that the Company and the Trustee may from time to time enter into one or more indentures supplemental to the First Mortgage as amended for the purposes, among other things which may be therein set forth, to mortgage or pledge additional property under the First Mortgage as amended and to establish the terms and provisions of any series of Bonds other than the 3½ % Series Due 1960; and

WHEREAS, the Company, pursuant to resolutions duly adopted by its Board of Directors at a meeting of said Board of Directors duly called and held, has determined under and in accordance with the provisions of the First Mortgage as amended and of this Forty-Fifth Supplemental Indenture to create a new series of Bonds to be known as its First Mortgage Bonds, Variable Rate Pollution Control Series 2007 Due 2040 (hereinafter sometimes called the New Bonds), which shall be limited to the aggregate principal amount of $90,000,000; and

WHEREAS, the New Bonds are to be issued by the Company to the Ohio Air Quality Development Authority (hereinafter called the Authority), or its assignee, to evidence and secure the obligations of the Company to repay the loan of the proceeds of the sale of the Project Bonds (as hereinafter defined) made by the Authority to the Company, pursuant to a certain Loan Agreement, dated as of November 1, 2007, between the Authority and the Company (hereinafter called the Loan Agreement), to assist in the financing of the Company’s portion of the cost of acquisition, construction and installation of certain “air quality facilities” (as that term is defined and used in Section 3706.01, of the Ohio Revised Code) installed in connection with: Units 7 and 8 at the Miami Fort Generating Station located in Hamilton County, Ohio as to which the Company at the date hereof owns an undivided 36% interest as tenant in common with another public utility company, Unit 2 at the Killen Generating Station located in Adams County, Ohio as to which the Company at the date hereof owns an undivided 67% interest as tenant in common with another public utility company, Units 1-4 at the J. M. Stuart Generating Station located in Brown and Adams Counties, Ohio as to which the Company at the date hereof owns an

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undivided 35% interest as tenant in common with two other public utility companies, and Unit 4 at the Conesville Generating Station in Coshocton County, Ohio as to which the Company at the date hereof owns an undivided 16.5% interest as tenant in common with two other public utility companies (such interests in said facilities being hereinafter called the Project); and

WHEREAS, the loan by the Authority in respect of the Project is to be funded by the proceeds derived from the sale by the Authority of State of Ohio Collateralized Air Quality Development Revenue Bonds, 2007 Series A (The Dayton Power and Light Company Project), in the aggregate principal amount of $90,000,000 (hereinafter called the Project Bonds); and

WHEREAS, the Project Bonds are to be issued under a certain Trust Indenture, dated as of November 1, 2007 (hereinafter called the Project Bonds Indenture), between the Authority and The Bank of New York, as Trustee (hereinafter in such capacity called the Project Bond Trustee), and the New Bonds are to be assigned by the Authority to the Project Bond Trustee as security for the payment of the principal of, and premium, if any, and interest on the Project Bonds and are to be delivered by the Company on behalf of the Authority directly to the Project Bond Trustee; and

WHEREAS, the New Bonds and the Trustee’s certificate to be endorsed on all the New Bonds are to be respectively and substantially in the forms established hereby and approved by the aforesaid resolutions, which are substantially in the form of Exhibit A hereto; and

WHEREAS, at a meeting of the Board of Directors of the Company, the Board of Directors adopted a resolution that authorized officers of the Company to approve the form, terms and provisions of this Forty-Fifth Supplemental Indenture (including the form of the New Bonds), and the execution by the Company of this Forty-Fifth Supplemental Indenture; and

WHEREAS, all things necessary to make the New Bonds hereinafter described, when duly authenticated by the Trustee and issued by the Company, valid, binding and legal obligations of the Company, and to make this Indenture a valid and binding agreement supplemental to the First Mortgage as amended, have been done and performed.

NOW, THEREFORE, THIS INDENTURE WITNESSETH

that, in order further to secure the payment of all the Bonds at any time issued and outstanding under the First Mortgage as amended or this Forty-Fifth Supplemental Indenture according to their tenor, purport and effect, as well the interest thereon as the principal thereof, and further to secure the performance and observance of all the covenants and conditions therein and in the First Mortgage as amended and herein contained, and further to set forth the terms and conditions upon which the New Bonds are to be issued, secured and held, and for and in consideration of the premises and of the acceptance or purchase of the New Bonds by the holders or registered owners thereof, and of the sum of one dollar, lawful money of the United States of America, to the Company duly paid by the Trustee at or before the ensealing and delivery of this Forty-Fifth Supplemental Indenture, the receipt whereof is hereby acknowledged, the Company has executed and delivered this Forty-Fifth Supplemental Indenture, and has granted, bargained,

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sold, released, conveyed, assigned, transferred, pledged, set over and confirmed, and by these presents does grant, bargain, sell, release, convey, assign, transfer, pledge, set over and confirm unto the Trustee, and to its successor or successors in said trust, and to it and its and their assigns forever, and does hereby subject to the lien of the First Mortgage as heretofore and hereby amended all the following described properties (all of which properties are included in and constitute a part of the “mortgaged property” and the “mortgaged and pledged property” as such terms are used and defined in the First Mortgage as heretofore and hereby amended and whenever used in the First Mortgage as heretofore and hereby amended such terms include and refer to such properties), to wit:

FIRST.

REAL PROPERTY AND INTERESTS IN REAL PROPERTY.

All and singular, all real property and interests in real property acquired by the Company between September 1, 2006, the date of the Forty-Fourth Supplemental Indenture, and the date of this Forty-Fifth Supplemental Indenture, and owned by the Company at the latter date.

SECOND.

ELECTRIC GENERATING PLANTS.

All electric generating plants and stations of the Company acquired by it between September 1, 2006, the date of the Forty-Fourth Supplemental Indenture, and the date of this Forty-Fifth Supplemental Indenture, and owned by it at the latter date, including all power houses, buildings, structures and works, and the land on which the same are situated, and all other lands and easements, rights-of-way, permits, privileges, towers, poles, wires, machinery, equipment, appliances, appurtenances and supplies forming a part of such plants and stations, or any of them, or occupied, enjoyed or used in connection therewith.

THIRD.

TRANSMISSION LINES.

All electric overhead and underground transmission lines of the Company acquired by it between September 1, 2006, the date of the Forty-Fourth Supplemental Indenture, and the date of this Forty-Fifth Supplemental Indenture, and owned by it at the latter date, including towers, poles, pole lines, conduits, manholes, switching devices, insulators, and other structures, appliances, devices and equipment, and all the property forming a part thereof or appertaining thereto, and all service lines extending therefrom, together with all real property, rights-of-way, easements, permits, privileges, franchises, and rights for or relating to the construction, maintenance or operation thereof, through, over, under or upon any private property or any public way within as well as without the corporate limits of any municipal corporation.

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FOURTH.

SUBSTATIONS AND SUBSTATION SITES.

All substations and switching stations of the Company acquired by it between September 1, 2006, the date of the Forty-Fourth Supplemental Indenture, and the date of this Forty-Fifth Supplemental Indenture, and owned by it at the latter date, for transforming or otherwise regulating electric current at any of its plants, together with all buildings, transformers, wires, cables, insulators, structures, appliances, devices, equipment and all other property, real or personal, forming a part of, or appertaining thereto, or used, occupied or enjoyed in connection with any of such substations and switching stations.

FIFTH.

ELECTRIC DISTRIBUTION SYSTEMS.

All electric distribution systems of the Company acquired by it between September 1, 2006, the date of the Forty-Fourth Supplemental Indenture, and the date of this Forty-Fifth Supplemental Indenture, and owned by it at the latter date, including substations, transformers, switchboards, towers, poles, wires, insulators, conduits, cables, manholes, appliances, devices, equipment and all other property, real or personal, forming a part of or appertaining thereto, or used, occupied or enjoyed in connection with such distribution systems or any of them, together with all rights-of-way, easements, permits, privileges, franchises, and rights in or relating to the construction, maintenance or operation thereof, through, over, under or upon any private property or public ways within as well as without the corporate limits of any municipal corporation.

SIXTH.

LIQUEFIED PETROLEUM GAS PRODUCTION AND STORAGE FACILITIES.

All additions to liquefied petroleum gas production plants and storage facilities of the Company acquired by it between September 1, 2006, the date of the Forty-Fourth Supplemental Indenture, and the date of this Forty-Fifth Supplemental Indenture, and owned by it at the latter date, including all buildings, structures, underground storage caverns, and works, and the land on which the same are situated, and all other lands and easements, rights-of-way, permits, privileges, pipe lines, machinery, equipment, appliances, appurtenances and supplies forming a part of such plants and stations, or any of them, or occupied, enjoyed or used in connection therewith.

SEVENTH.

GAS DISTRIBUTION SYSTEMS.

All gas distribution systems of the Company acquired or constructed by it between September 1, 2006, the date of the Forty-Fourth Supplemental Indenture, and the date of this

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Forty-Fifth Supplemental Indenture, and owned by it at the latter date, for distribution of gas, including pipes, mains, conduits, meters, appliances, equipment, and all other property, real or personal, forming a part of or appertaining to or used, occupied or enjoyed in connection with such distribution systems, or any of them, together with all rights-of-way, easements, permits, privileges, franchises and rights, for or relating to the construction, maintenance or operation thereof, through, over, under or upon any private property or any public streets or highways, within as well as without the corporate limits of any municipal corporation.

EIGHTH.

OFFICE AND DEPARTMENTAL BUILDINGS.

All office and departmental buildings of the Company, including the real estate on which such structures stand, acquired by it between September 1, 2006, the date of the Forty-Fourth Supplemental Indenture, and the date of this Forty-Fifth Supplemental Indenture, and owned by it at the latter date, appertaining to, used, occupied or enjoyed in connection with the rendition of public utility service.

NINTH.

TELEPHONE LINES.

All telephone lines of the Company acquired by it between September 1, 2006, the date of the Forty-Fourth Supplemental Indenture, and the date of this Forty-Fifth Supplemental Indenture, and owned by it at the latter date, used or available for use in the operation of its properties or otherwise.

TENTH.

FRANCHISES.

All and singular the franchises, grants, immunities, privileges and rights of the Company granted to or acquired by it between September 1, 2006, the date of the Forty-Fourth Supplemental Indenture, and the date of this Forty-Fifth Supplemental Indenture, and to which it was entitled at the latter date, including all and singular the franchises, grants, immunities, privileges and rights of the Company granted by all municipalities or political subdivisions, and all right, title and interest therein owned by the Company on the date of the execution of this Forty-Fifth Supplemental Indenture, and all renewals, extensions and modifications of said franchises, grants, immunities, privileges and rights, or any of them, and of all other franchises, grants, immunities, privileges and rights now subject to the lien of the First Mortgage as amended.

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ELEVENTH.

OTHER REAL ESTATE AND APPURTENANCES.

A.                                    All other real estate and interests in real estate and all other physical electric power and light, gas and other property owned by the Company at the date of execution of this Forty-Fifth Supplemental Indenture.

B.                                      All other real estate and interests in real estate and all other physical electric power and light, gas and other property which the Company may hereafter acquire or construct.

C.                                      All present and future appurtenances of the real estate and interests in real estate which now are, or hereafter shall be, subject to the lien of the First Mortgage as amended, and all plants, works, buildings, structures, fixtures, improvements, betterments and additions now owned, or hereafter acquired or constructed by the Company, upon any of the real estate which, or interests in which, now are or hereafter shall be subject to the lien of the First Mortgage as amended.

D.                                     All corporate rights, privileges, immunities and franchises, powers, licenses, easements, leases, contracts and other rights and all renewals and extensions thereof held or acquired for use or used upon, or in connection with or appertaining to, any of the properties which now are or hereafter shall be subject to the lien of the First Mortgage as amended, or which the Company has or may have the right to exercise in respect of any of said properties.

E.                                       All machinery, tools and equipment now owned or hereafter acquired by the Company, which now or hereafter belong or appertain to or are used in connection with the plants, works, transmission lines, distribution systems, buildings, structures and fixtures which now are or hereafter shall be subject to the lien of the First Mortgage as amended.

Together with all and singular the tenements, hereditaments and appurtenances belonging or in any way appertaining to the aforesaid property or any part thereof, with the reversion and reversions, remainder and remainders, rents, issues, income and profits thereof, and all the estate, right, title, interest and claim whatsoever at law or in equity, which the Company now has or which it may hereafter acquire in and to the aforesaid property and every part and parcel thereof.

It is not intended to include in the lien of the First Mortgage as amended and this grant shall not be deemed to apply (1) to any revenues, earnings, rents, issues, income or profits of the mortgaged property, or any cash (except cash deposited with the Trustee pursuant to any of the provisions of the First Mortgage as heretofore and hereby amended), or any bills, notes or accounts receivable, contracts or choses in action, or any materials or supplies or construction equipment, or any merchandise, equipment or apparatus manufactured or acquired for the purpose of sale or resale in the usual course of business, except in case of the happening of a completed default as defined in Section 1 of Article Twelve of the First Mortgage as heretofore and hereby amended, and following such completed default, in case the Trustee or a receiver or trustee shall enter upon and take possession of the mortgaged property, or (2) in any case, to any cars, trucks or other vehicles of any nature for the transportation of personnel, materials or equipment by any means which may have been acquired after the effective date of the

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amendment to this Clause made by or pursuant to the provisions of the Eleventh Supplemental Indenture, or to any bonds, notes, evidences of indebtedness, shares of stock or other securities, except such as may be specifically subjected to the lien of the First Mortgage as amended.

TWELFTH.

PROPERTY HEREAFTER TO BECOME SUBJECT TO THE LIEN OF THE FIRST MORTGAGE AS AMENDED.

A.                                    Any and all property, real, personal and mixed, including franchises, grants, immunities, privileges and rights, which the Company may hereafter acquire or to which it may hereafter become entitled,