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                                                                     EXHIBIT 5.1


                                                     December 11, 1998


Protection One Alarm Monitoring, Inc.
Protection One, Inc.
6011 Bristol Parkway
Culver City, California  90230

Ladies and Gentlemen:

         We have acted as counsel to Protection One Alarm Monitoring, Inc., a
Delaware corporation (the "Issuer"), and Protection One, Inc., a Delaware
corporation ("POI"), in connection with the preparation and filing by the Issuer
and POI of a Registration Statement on Form S-4 (Registration No. 333-64021)
(the "Registration Statement") filed with the Securities and Exchange Commission
on September 22, 1998 under the Securities Act of 1933, as amended (the "Act"),
relating to the Issuer's $250,000,000 aggregate principal amount of 7 3/8%
Senior Notes due 2005 (the "New Notes") that are to be issued in exchange for a
like principal amount of the issued and outstanding 7 3/8% Senior Notes due 2005
(the "Old Notes") of the Issuer. The Issuer proposes to offer, upon the terms
set forth in the prospectus contained in the Registration Statement, to exchange
$1,000 principal amount of New Notes for each $1,000 principal amount of Old
Notes (the "Exchange Offer"). POI will fully, unconditionally and jointly and
severally guarantee (the "Guarantee") the New Notes on an unsecured, senior
basis. The New Notes and the Guarantee will be issued under the Indenture (the
"Indenture"), dated as of August 17, 1998, by and among the Issuer, POI, two
former guarantors which have merged into the issuer, and The Bank of New York,
as trustee (the "Trustee"). Capitalized terms defined in the Registration
Statement and not otherwise defined herein are used herein as so defined.

         In so acting, we have examined originals or copies, certified or
otherwise identified to our satisfaction, of the Indenture, the form of the New
Notes set forth in the Indenture and such corporate records, agreements,
documents and other instruments, and such certificates or comparable documents
of public officials and of officers and representatives of the Issuer and the
Guarantors and have made such inquiries of such officers and representatives as
we have deemed relevant and necessary as a basis for the opinion hereinafter set
forth.

         In such examination, we have assumed the genuineness of all signatures,
the legal capacity of natural persons, the authenticity of all documents
submitted to us as originals, the conformity to original documents of documents
submitted to us as certified or photostatic copies and the authenticity of the
originals of such latter documents. As to all questions of fact material to this
opinion that have not been independently established, we have relied upon
certificates or comparable documents of officers and representatives of the
Issuer and POI.
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Protection One Alarm Monitoring, Inc.
Protection One, Inc.
December 11, 1998
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           Based on the foregoing, and subject to the qualifications stated
herein, we are of the opinion that:

         1. The New Notes have been duly authorized by the Issuer for issuance
and, when executed by the Issuer and authenticated by the Trustee in accordance
with the terms of the Indenture, and delivered in exchange for the Old Notes in
accordance with the Exchange Offer, will be legal, valid and binding obligations
of the Issuer, enforceable against it in accordance with their terms, subject to
applicable bankruptcy, insolvency, fraudulent conveyance, reorganization,
moratorium and similar laws affecting creditors' rights and remedies generally,
and subject, as to enforceability, to general principles of equity, including
principles of commercial reasonableness, good faith and fair dealing (regardless
of whether enforcement is sought in a proceeding at law or in equity); and

         2. The Guarantee of POI has been duly authorized by POI, and when (i)
the New Notes issuable upon consummation of the Exchange Offer have been duly
executed by the Issuer and authenticated by the Trustee in accordance with the
terms of the Indenture, and (ii) the New Notes issuable upon consummation of the
Exchange Offer have been duly delivered against receipt of Old Notes surrendered
in exchange therefor, the Guarantee of New Notes issuable upon consummation of
the Exchange Offer will, when executed and delivered in accordance with the
Indenture, constitute the legal, valid and binding obligation of POI,
enforceable against it in accordance with its terms, subject to applicable
bankruptcy, insolvency, fraudulent conveyance, reorganization, moratorium and
similar laws affecting creditors' rights and remedies generally, and subject, as
to enforceability, to general principles of equity, including principles of
commercial reasonableness, good faith and fair dealing (regardless of whether
enforcement is sought in a proceeding at law or in equity).

         The opinion expressed herein is limited to the laws of the State of New
York and the corporate Laws of the State of Delaware and we express no opinion
as to the effect on the matters covered by this letter of the laws of any other
jurisdiction.

         We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and the reference to this firm under the caption "Legal
Matters" in the Prospectus forming a part of the Registration Statement.

                                                 Very truly yours,

                                                 /s/ Weil Gotshal & Manges LLP