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[LETTERHEAD OF APPLEBY SPURLING & KEMPE]

                                                                     EXHIBIT 5.1

                                                           E-mail: mjones@ask.bm
                                                                 MLJ/af/73287.77

                                                               14 September 2000

Tyco International Ltd.
The Zurich Centre, Second Floor
90 Pitts Bay Road
Pembroke HM 08
Bermuda

RE: REGISTRATION STATEMENT ON FORM S-3

Ladies and Gentlemen:

    We have acted as Bermuda counsel to Tyco International Ltd., a Bermuda
company ("Tyco" or the "Company"), in connection with the filing by Tyco and
Tyco International Group S.A., a Luxembourg company (the "Issuer"), with the
United States Securities and Exchange Commission of a Registration Statement on
Form S-3, File Nos. 333-44100 and 333-44100-01, (as amended, the "Registration
Statement"), with respect to (i) the Issuer's unsecured debt securities (the
"Debt Securities"), (ii) the guarantees (the "Guarantees") of the Debt
Securities by Tyco and (iii) the Tyco common shares to be issued upon conversion
or exchange of the Debt Securities (the "Common Shares"), to be issued from time
to time pursuant to Rule 415 under the United States Securities Act of 1933, as
amended (the "Securities Act"), for an aggregate initial offering price not to
exceed US$3,500,000,000. The Debt Securities are to be issued in one or more
series pursuant to Indentures among the Issuer, Tyco (as Guarantor) and the
trustees thereunder.

    For the purposes of this opinion we have examined and relied upon the
documents listed, and in some cases defined, in the Schedule to this opinion
(the "Documents").

    Unless otherwise defined herein, terms defined in the Registration Statement
and the Prospectus, have the same meanings when used in this opinion.

ASSUMPTIONS

    In stating our opinion we have assumed:

        (a) the authenticity, accuracy and completeness of all Documents
    submitted to us as originals and the conformity to authentic original
    Documents of all Documents submitted to us as certified, conformed,
    notarised, faxed or photostatic copies;

        (b) the genuineness of all signatures on the Documents;

        (c) that any factual statements made in any of the Documents are true,
    accurate and complete;

        (d) that the records which were the subject of the Company Search were
    complete and accurate at the time of such search and disclosed all
    information which is material for the purposes of this opinion and such
    information has not since the date of the Company Search been materially
    altered; and

        (e) that the records which were the subject of the Litigation Search
    were complete and accurate at the time of such search and disclosed all
    information which is material for the purposes
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    of this opinion and such information has not since the date of the
    Litigation Search been materially altered.

OPINION

    Based upon and subject to the foregoing, and subject to the reservations
mentioned below and to any matters not disclosed to us, we are of the opinion:

        1. Tyco is a limited liability company validly organized and existing
    and in good standing under the laws of Bermuda.

        2. When issued and paid for pursuant to the terms of any duly adopted
    Board resolutions of Tyco which have authorised their issue in accordance
    with the terms and conditions referred to or summarised in the Prospectus
    and the Registration Statement, Tyco's Common Shares issued upon conversion
    or exchange of the Debt Securities will be validly issued, fully paid and
    non-assessable.

        3. When a resolution of the Board of Tyco has been duly adopted to
    approve the creation of and the issue of the Guarantees upon the terms of
    the applicable Indenture, or any supplemental indenture conforming thereto
    and to applicable law, and to authorize the execution and delivery thereof,
    all necessary action required to be taken by Tyco pursuant to Bermuda law
    will have been taken by or on behalf of Tyco for the issue by Tyco of the
    Guarantees.

        4. No filing with, or authorisation, approval, consent, licence, order,
    registration, qualification or decree of, any court or governmental
    authority or agency in Bermuda is necessary or required to be made or
    obtained by Tyco in connection with the issue by Tyco of the Guarantees.

        5. There are no taxes, duties, or other charges payable to or chargeable
    by the Government of Bermuda, or any authority or agency thereof, in respect
    of the issue by Tyco of the Guarantees or the Common Shares.

RESERVATIONS

    We have the following reservations:

        (1) We are admitted to practise law in the Islands of Bermuda and we
    express no opinion as to any law other than Bermuda law, and none of the
    opinions expressed herein relates to compliance with or matters governed by
    the laws of any jurisdiction except Bermuda. This opinion is limited to
    Bermuda law as applied by the courts of Bermuda at the date hereof.

        (2) Any reference in this opinion to Tyco being in "good standing" shall
    mean for the purposes of this opinion that it has been issued with a
    Certificate of Compliance by the Registrar of Companies as at the date
    hereinbefore mentioned.

        (3) Any reference in this opinion to shares being "non-assessable" shall
    mean, in relation to fully paid shares of Tyco and subject to any contrary
    provision in any agreement in writing between such company and the holder of
    such shares, that no shareholder shall be bound by an alteration to the
    Memorandum of Association or Bye-Laws of Tyco after the date on which he or
    she became a shareholder, if and so far as the alteration requires him or
    her to take, or subscribe for additional shares, or in any way increases his
    or her liability to contribute to the share capital of, or otherwise to pay
    money to, Tyco.

DISCLOSURE

    This opinion is addressed to you in connection with the filing by the
Company of the Registration Statement with the Securities and Exchange
Commission.

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    We consent to the inclusion of this opinion as an exhibit to the
Registration Statement. We also consent to the reference to our firm under the
caption "Legal Matters" in the Prospectus included as part of the Registration
Statement.

    This opinion is to be governed by and construed in accordance with the laws
of Bermuda and shall not give rise to legal proceedings in any jurisdiction
other than Bermuda.

Yours faithfully,

/s/ APPLEBY SPURLING & KEMPE
---------------------------------
Appleby Spurling & Kempe

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                                    SCHEDULE

 (i) a Certificate of Compliance issued by the Registrar of Companies in Bermuda
     on 1 August 2000 in respect of Tyco;

 (ii) the Certificate of Incorporation, Memorandum of Association and Bye-laws
      of Tyco;

(iii) a copy of the Registration Statement, excluding the documents incorporated
      by reference therein;

 (iv) copies of the pages of the Registration Statement as initially filed
      signed by all of the Directors of Tyco (the "Signature Pages");

 (v) a copy of the form of Senior Indenture previously filed as Exhibit 4.1 to
     the Registration Statement on Form S-3 dated June 9, 1998 pursuant to which
     the Debt Securities may be issued;

 (vi) a copy of the form of Subordinated Indenture previously filed as
      Exhibit 4.2 to the Registration Statement on Form S-3 pursuant to which
      the Debt Securities may be issued (together with the Senior Indenture, the
      "Indentures");

(vii) The entries and filings shown in respect of Tyco on the file of the
      Company maintained in the Register of Companies at the office of the
      Registrar of Companies in Hamilton, Bermuda, as revealed by a search on 14
      September 2000 (the "Company Search"); and

(viii) The entries and filings shown in the Supreme Court Causes Book maintained
       at the Registry of the Supreme Court in Hamilton, Bermuda, as revealed by
       a search on 14 September 2000 in respect of Tyco (the "Litigation
       Search").

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