Document:

Exhibit 4.16

                               AMENDING AGREEMENT

      THIS AMENDING AGREEMENT made effective as of April 23, 2004.

BETWEEN:

            MITEL NETWORKS  CORPORATION,  a corporation  incorporated  under the
            laws of Canada,

            (the "Corporation")

                                     - and -

            ZARLINK  SEMICONDUCTOR  INC., a corporation  incorporated  under the
            laws of Canada,

            ("Zarlink")

RECITALS:

A.    The Corporation  and Zarlink are party to a supply  agreement (the "Supply
      Agreement") dated February 16, 2001, as amended.

B.    Clause  21(A)(ii)  of  the  Supply  Agreement  provides  that  the  Supply
      Agreement  may  be   terminated   by  one  party  in  certain   prescribed
      circumstances  where a change occurs in the  constitution or circumstances
      of the other party, as more particularly set forth therein.

C.    In connection with a proposed financing  transaction pursuant to which new
      investors of the Corporation  will subscribe for certain  preferred shares
      in the capital of the  Corporation  (the  "Financing"),  and in connection
      with which the  Corporation  proposes to effect certain  amendments to its
      constating  documents  as set out in the  management  proxy  circular  and
      related  shareholder  meeting materials of the Corporation dated March 26,
      2004  (the  "Meeting  Materials"),  a copy of which has been  provided  to
      Zarlink,  the  Corporation  and  Zarlink now desire to provide for certain
      acknowledgements and amendments with respect to the Supply Agreement.

THEREFORE THE PARTIES AGREE AS FOLLOWS:

1.    Acknowledgement

            Zarlink  hereby  acknowledges  and  agrees,  for  purposes of clause
            21(A)(ii) of the Supply Agreement, that:

      (a)   the  Corporation  proposes  to  effect  certain  amendments  to  its
            constating documents in connection with the Financing, substantially
            as described in the Meeting Materials;

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                                       2

      (b)   such proposed amendments are not materially detrimental to Zarlink's
            interests and will not impede the Corporation's ability to carry out
            its obligations under the Supply Agreement; and

      (c)   such proposed  amendments  shall not give rise to a right of Zarlink
            to terminate the Supply Agreement.

2.    Amendment

      The Supply  Agreement is hereby  amended as follows:  Clause  21(A)(ii) is
      hereby deleted in its entirety.

3.    Binding Amendment

      This   Amending   Agreement,   being  duly   executed  by  an   authorized
      representative of each of the Corporation and Zarlink, constitutes a valid
      and binding  amendment to the Supply  Agreement in accordance with section
      32 thereof.

4.    General

      (a)   This Amending  Agreement  and the Supply  Agreement  constitute  the
            entire  agreement  between the parties  with  respect to the subject
            matter  hereof  and  thereof  and  cancel  and  supersede  any prior
            understandings  and  agreements  between the parties with respect to
            such  subject  matter.  There  are no  representations,  warranties,
            terms, conditions,  undertakings or collateral agreements,  express,
            implied or statutory, between the parties to this Amending Agreement
            other  than  those  expressly  set forth  herein  and in the  Supply
            Agreement.

      (b)   Except as provided in this Amending Agreement, in all other respects
            the Supply Agreement remains in full force and effect.

      (c)   Each of the parties  hereto shall with  reasonable  diligence do all
            such  things and provide all such  reasonable  assurances  as may be
            required  to  consummate  the  transactions   contemplated  by  this
            Amending  Agreement,  and each  party  shall  provide  such  further
            documents  or  instruments  required  by any  other  party as may be
            reasonably  necessary  or  desirable  to effect the  purpose of this
            Amending Agreement and carry out its provisions.

      (d)   This Amending  Agreement  shall be construed in accordance  with the
            laws of the  Province of Ontario  and the laws of Canada  applicable
            therein and shall be treated in all respects as an Ontario contract.

      (e)   This  Amending  Agreement  may be executed in several  counterparts,
            each of which,  when executed by a party hereto,  shall be deemed to
            be an original and such counterparts  shall together  constitute one
            and the same instrument.

<PAGE>
                                       3

IN WITNESS OF WHICH the parties have executed this Amending Agreement.

                                      MITEL NETWORKS CORPORATION

                                        By:
                                            ------------------------------------
                                            Name:
                                            Title:

                                      ZARLINK SEMICONDUCTOR INC.

                                        By:
                                            ------------------------------------
                                            Name:
                                            Title:Exhibit 4.22

                                    AMENDMENT

THIS AMENDMENT is made September 20, 2003 among:

      March Networks  Corporation,  a Canadian business  corporation  having its
      offices  at  Tower  B,  555  Legget  Drive,  Ottawa,  ON K2K  2X3  ("March
      Networks")

-and-

      Mitel Networks  Corporation,  a Canadian business  corporation  having its
      offices at 350 Legget Drive, Ottawa, ON K2K 2W7 ("Mitel Networks")

-and-

      Mitel Networks  International  Limited, a Barbadian  business  corporation
      having its offices at Charnic Business Centre,  Spring Garden Highway, St.
      Michael, Barbados ("MNIL")

-and-

      Mitel Networks Limited,  a UK business  corporation  having its offices at
      Mitel Business Park, Portskewett, Caldicott, UK NPZ6 5YR ("MNL")

WHEREAS:

A.    March  Networks,  Mitel  Networks,  MNIL and MNL entered  into an alliance
      agreement  effective as of September 21, 2001 (the  "Alliance  Agreement")
      with a term of two years, expiring on September 20, 2003.

B.    Pursuant to Section 9.1 of the  Alliance  Agreement,  the parties  wish to
      renew the  Alliance  Agreement  on the same terms and  conditions  for one
      additional year term expiring on September 20, 2004.

NOW THEREFORE for good and valuable  consideration,  the receipt and sufficiency
of which is hereby  acknowledged,  the parties to this Amendment hereby agree as
follows:

1.    The  term of the  Alliance  Agreement  is  hereby  extended  for one  year
      expiring September 20, 2004.

<PAGE>

2.    All terms and conditions of the Alliance Agreement to remain the same.

IN WITNESS WHEREOF the parties hereto have caused this Amendment to be signed by
their duly authorized representatives as of the date written above.

Mitel Networks Corporation                  March Networks Corporation

_________________________________           ___________________________________

_________________________________           ___________________________________

_________________________________           ___________________________________

Mitel Networks International Limited        Mitel Networks Limited

_________________________________           ___________________________________

_________________________________           ___________________________________

_________________________________           ___________________________________Exhibit 4.26

[Flag and TPC logo in English and French]

March 27, 2003

                                                  TPC File Reference: 720-481443

Mr. Don Smith
Chief Executive Officer
Mitel Networks Corporation
350 Legget Drive
Kanata, Ontario
K2K 2W7

Dear Mr. Smith:

Re:   Development of Smart Broadband Appliances and a Suite of Interactive
      Applications

I am pleased to inform you that  approval has been granted to delete,  by way of
this letter,  the annual  contribution  disbursement  limit of  $28,000,000  for
Fiscal Year  2002-2003  specified in section 4.3 of Article 4 of the  Technology
Partnerships  Canada  (TPC)  /  Mitel  Networks   Corporation,   March  Networks
Corporation,  and Mitel  Knowledge  Corporation  Contribution  Agreement for the
above-captioned  project.  This will  allow TPC to pay  additional  claims  this
fiscal year.

                                            Yours sincerely,

                                            Jacques Cloutier
                                            Acting Director
                                            Enabling Technologies

[TPC letterhead                                                 with maple leaf]

<PAGE>

                                                      TPC PROJECT NO. 720-481443
                                                                 AMENDMENT NO. 2

                         TECHNOLOGY PARTNERSHIPS CANADA

                               AMENDMENT AGREEMENT

This Agreement made

Between:   HER MAJESTY THE QUEEN IN RIGHT OF CANADA,
           as represented by the Minister of Industry
           (hereinafter referred to as the "Minister")

And:       MARCH NETWORKS CORPORATION
           (hereinafter referred to as "a Proponent" or "March Networks").

And:       MITEL NETWORKS CORPORATION
           (hereinafter referred to as "a Proponent" or "Mitel Networks")

And:       MITEL KNOWLEDGE CORPORATION
           (hereinafter referred to as "a Proponent" or "Mitel Knowledge")

Collectively referred to as "the Proponents".

INTRODUCTION

(i)   The Minister and the Proponents entered into a Contribution Agreement
      dated the 10th day of October, 2002 under the Technology Partnerships
      Canada Program (the "Contribution Agreement"); and

(ii)  The Contribution Agreement was amended by letter dated March 27, 2003, now
      called Amendment Number 1; and

(iii) The Minister and the Proponents now wish to amend the Contribution
      Agreement.

In consideration of their respective obligations set out in the Contribution
Agreement, the parties agree to amend the Contribution Agreement as follows:

<PAGE>

                                                                          Page 2

1.    This Amendment must be signed by the Recipient and received by the
      Minister within thirty (30) days of its signature on behalf of the
      Minister, failing which it will be null and void.

2.    In Article 3.2:

      DELETE:            the date "September 30th, 2004"; and
      REPLACE:           with the date "March 31st, 2005".

3.    In Article 4.3:

      DELETE:            the Fiscal Year Contribution amounts in their entirety;
      REPLACE:           and with the following Fiscal Year Contribution
                         amounts:

                         "2002/2003      $29,577,660
                          2003/2004      $15,440,000
                          2004/2005      $14,982,340".

4.    In Article 7.2:

      DELETE:            the name "Dr. Donald Mills" and the title "Chief
                         Operating Officer" for March Networks Corporation, and
      REPLACE:           with the name "Peter Strom" and the title "President
                         and Chief Executive Officer".

5.    In Article 8.1:

      DELETE:            the date "September 30th, 2004"; and
      REPLACE:           with the date "March 31st, 2005".

6.    In Schedule 8, Article 4.8:

      DELETE:            the name "Dr. Donald Mills" and the title "Chief
                         Operating Officer" for March Networks Corporation, and
      REPLACE:           with the name "Peter Strom" and the title "President
                         and Chief Executive Officer".

All provisions of the Contribution Agreement remain in full force and effect,
except as modified by this Amendment Agreement.

                                                            File No.: 720-481443

<PAGE>

                                                                          Page 3

IN WITNESS WHEREOF the parties hereto have executed this Amendment Agreement
through duly authorized representatives.

HER MAJESTY THE QUEEN IN RIGHT
OF CANADA, as represented by the Minister of Industry

Per:     "Denise Guevremont"                                 "April 27, 2004"
         --------------------------------------              ----------------
         Technology Partnerships Canada                       Date

         "Denise Guevremont - Director"
         Name & Title

MARCH NETWORKS CORPORATION]

Per:     "Peter Strom"                                        "May 02, 2004"
         --------------------------------------               --------------
                                                              Date

         "Peter Strom - President / CEO"
         --------------------------------------
         Name & Title

MITEL NETWORKS CORPORATION]

Per:     "Don Smith"                                          "29 April 2004"
         --------------------------------------               --------------
                                                              Date

         "Don Smith, CEO"
         Name & Title

MITEL KNOWLEDGE CORPORATION]

Per:     "Jose Medeiros"                                      "April 30, 2004"
         --------------------------------------               --------------
                                                              Date

         "Jose Medeiros, CFO"
         --------------------------------------
         Name & Title

                                                            File No.: 720-481443

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