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                                                                    EXHIBIT 4.24

                            SECOND AMENDING AGREEMENT

      MEMORANDUM OF AGREEMENT made as of the 7th day of February, 2005.

 BETWEEN:

                  MITEL NETWORKS CORPORATION,

                  a corporation incorporated under the laws of Canada, as
                  borrower

                  (hereinafter referred to as the "BORROWER")

                                        -and-

                  THE LENDERS FROM TIME TO TIME PARTIES TO THE CREDIT AGREEMENT,

                  (hereinafter referred to as the "LENDERS")

                                         -and-

                  BANK OF MONTREAL,

                  a Canadian chartered bank, as Administrative Agent and Lead
                  Arranger

                  (hereinafter referred to in its own capacity as "BMO" and in
                  its capacity as administrative agent on behalf of the Lenders,
                  as the "ADMINISTRATIVE AGENT").

            WHEREAS pursuant to an amended and restated credit agreement made as
of the 21st day of April, 2004 (the "ORIGINAL AGREEMENT"), a revolving credit
facility was made available to the Borrower upon and subject to the terms and
conditions therein set forth;

            AND WHEREAS the Borrower and Lenders made certain amendments to the
Original Agreement by an amending agreement dated as of July 24, 2004 (the
Original Agreement, as so amended, being hereinafter referred to as the "CREDIT
AGREEMENT");

            AND WHEREAS the Borrower and the Lenders have agreed to amend the
Credit Agreement by executing and delivering this Amending Agreement;

            NOW THEREFORE THIS AGREEMENT WITNESSES that, in consideration of the
premises, the covenants herein contained and other valuable consideration, the
parties hereto agree as follows:

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l.    The Credit Agreement is hereby amended in the following respects:

      (a)   The definition of "Available Amount" in Section 1.1 of the Credit
            Agreement is deleted and replaced with the following:

            ""AVAILABLE AMOUNT" means, at any time, the lesser of:

            (a)   the Committed Amount or its Equivalent Amount in U.S. Dollars;

            (b)   the Borrowing Base; and

            (c)   (i)  if the Barclays Facility has been entered into, Cdn.
                       $20,000,000, or

                  (ii) if the Barclays Facility has not been entered into or
                       has been fully and finally terminated and repaid in full
                       and any security granted in connection therewith has been
                       released, Cdn. $25,000,000,

                  or, in each case, the Equivalent Amount in U.S. Dollars;";

      (b)   Section 1.1 of the Credit Agreement is amended by adding the
            following definition:

            ""BARCLAYS FACILITY" shall mean a working capital credit facility to
            be entered into between MNL and Barclays Bank plc in an aggregate
            amount not exceeding (pound)10,000,000 (including a (pound)10
            million chattel mortgage charging assets of MNL only to be granted
            by MNL in favour of Barclays Bank plc, as amended, restated,
            supplemented or replaced from time to time with the consent of the
            Required Lenders);";

      (c)   The definition of "Borrowing Base" in Section 1.1 of the Credit
            Agreement is deleted and replaced with the following:

            "BORROWING BASE" shall mean, at any time, the sum of:

            (i)   50% of Eligible Accounts Receivable; plus

            (ii)  90% of EDC Receivables; plus

            (iii) 100% of trade accounts of the Borrower and the Guarantors
                  which are secured by bank letters of credit or guarantee
                  satisfactory to the Required Lenders which bank letters of
                  credit or guarantees shall have been assigned to the
                  Administrative Agent if so requested by the Administrative
                  Agent;

            For purposes of calculating the Borrowing Base, Eligible Accounts
            Receivable and EDC Receivables of the Borrower and the Guarantors
            shall be expressed in

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            Canadian Dollars based on the Equivalent Amount of the value of any
            such amounts in U.S. Dollars, Sterling or Euros;";

      (d)   The definition of "Permitted Debt" in Section 1.1 of the Credit
            Agreement shall be amended by adding the following paragraph
            immediately following paragraph (x) thereof:

            "(xi) Debt for borrowed money in an aggregate amount not exceeding
                  (pound)10,000,000 incurred pursuant the Barclays Facility;"

            and re-numbering subsequent paragraphs, and all references thereto,
            as appropriate to reflect such addition;

      (e)   Section 2.7(c) of the Credit Agreement is deleted in its entirety;

      (f)   Section 8.3 of the Credit Agreement is deleted and replaced with the
            following:

           "8.3  FINANCIAL COVENANT

                  The Borrower covenants and agrees with the Administrative
            Agent and the Lenders that, unless the Administrative Agent and the
            Required Lenders otherwise consent in writing, so long as any amount
            payable hereunder is outstanding, the Borrower shall not permit its
            EBTTDA (determined on a consolidated basis in accordance with GAAP
            as in effect on the date of this Agreement and measured as at the
            last day of each fiscal quarter of the Borrower for such fiscal
            quarter then ending, commencing with the fiscal quarter ending July
            25, 2004 and, to the extent that any assets or liabilities of
            Endurance Trust are included in the consolidated financial
            statements of the Borrower, calculated without reference to the
            assets and liabilities of Endurance Trust) to be less than the
            following amounts for the relevant fiscal quarter as set forth
            below:

            (i)   for the fiscal quarter ending July 25,2004, negative Cdn.
                  $5,000,000;

            (ii)  for the fiscal quarter ending October 24,2004, Cdn. $0.00;

            (iii) for the fiscal quarter ending January 23,2005, Cdn.
                  $3,000,000; and

            (iv)  for the fiscal quarter ending April 24,2005, negative U.S.
                  $5,000,000.";

      (g)   Section 8.4 is added to the Credit Agreement as follows:

            "8.4  RIGHT OF FIRST REFUSAL

            In consideration of the Lender agreeing to amend the credit
            facility, inter alia, to increase the Available Amount and to permit
            MNL to incur additional indebtedness in an amount up to
            (pound)10,000,000 to Barclays Bank plc, the Borrower

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            covenants and agrees with the Lender that BMO Nesbitt Burns or any
            other affiliate of the Lender, in each case either alone or in
            combination with any other affiliate of the Lender, shall have a
            right of first refusal to act, at its option:

            (a)   as the lead in connection with any transaction undertaken in
                  Canada or as a co-lead and lead Canadian underwriter or agent
                  in connection with any transactions undertaken outside Canada
                  for both private and public offerings of equity or debt; and

            (b)   as an advisor on any sell-side M&A transaction involving asset
                  sales, including the sale of the company should a formal sales
                  process be initiated by the Borrower where an investment
                  banker is engaged to manage the sale process and seek
                  potential buyers, but excluding, at the Borrower's option,
                  responding to an unsolicited bid resulting from an
                  introduction from another investment bank or advisory firm.

            The rights of first refusal herein granted are conditional upon such
            underwriting and investment banking services being offered to the
            Borrower on terms and conditions (including price) which are
            generally consistent with then-current market terms and conditions
            for companies in similar industries and of similar size. The
            agreement of the Borrower under this Section 8.4 shall survive
            termination of this Agreement and shall remain in full force and
            effect as an enforceable obligation of the Borrower during the term
            of this Agreement and for a period of six months following the
            scheduled maturity of this Agreement."; and

      (h)   Section (xviii) of the definition of "Permitted Encumbrance" in
            Schedule F to the Credit Agreement is deleted and replaced with the
            following:

            "(xviii)Liens granted in connection with obligations incurred
                    pursuant to clause (x), (xi) or (xii) of the definition of
                    Permitted Debt;".

2. This Amending Agreement may be executed in counterparts, each of which shall
be considered an original and all of which taken together shall constitute a
single agreement.

3. This Amending Agreement shall be governed by the laws of the Province of
Ontario and the federal laws of Canada applicable therein.

4. The Credit Agreement, as amended, is hereby confirmed.

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      IN WITNESS WHEREOF the parties hereto have executed this Amending
Agreement.

                                     MITEL NETWORKS
                                     CORPORATION

                                     by /s/ Steve Spooner
                                        ------------------------
                                        Name: Steve Spooner
                                        Title: C.F.O

                                     BANK OF MONTREAL, as
                                     Administrative Agent And Lead Arranger

                                     by /s/ Ashok Rao
                                        ------------------------
                                        Name: Ashok Rao
                                        Title: Vice President

                                     BANK OF MONTREAL, as Lender

                                     by /s/ Ashok Rao
                                        -------------------------
                                        Name: Ashok Rao
                                        Title: Vice President