Exhibit 4.23

                           PURCHASE AND SALE AGREEMENT

                                     BETWEEN

                           MITEL KNOWLEDGE CORPORATION
                                       AND
                           MITEL NETWORKS CORPORATION

                                   DATED AS OF
                                NOVEMBER 1, 2002

                                November 1, 2002



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                           PURCHASE AND SALE AGREEMENT

      THIS AGREEMENT is entered into as of November 1, 2002, BETWEEN:

      Mitel Knowledge Corporation,  a corporation incorporated under the laws of
      Canada ( "MKC"),

- and -

      Mitel Networks Corporation,  a corporation  incorporated under the laws of
      Canada ( "MNC"),

WHEREAS:

A.  MKC  and MNC  executed  a  Research  and  Development  Agreement  (the  "R&D
Agreement"),  effective as of March 27, 2001, pursuant to which MKC retained MNC
to perform certain research and development work;

B. MKC and MNC have  agreed to  terminate  the R&D  Agreement,  as provided in a
Termination Agreement dated November 1, 2002;

               NOW THEREFORE, the parties hereto agree as follows:

                           ARTICLE 1 - INTERPRETATION

1.01 Definitions

      In this Agreement,  the following  capitalized terms and expressions shall
have the meanings hereinafter ascribed thereto:

      (a)   "Act" means the Income Tax Act (Canada), as amended;

      (b)   "Agreement"  means  this  agreement,   including  its  recitals  and
            schedules, as amended from time to time;

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      (c)   "Effective  Time" means 2:00 p.m.  Eastern Standard Time on November
            1, 2002;

      (d)   "Laws" means legally binding laws, statutes,  by-laws and ordinances
            of any Governmental Authority having jurisdiction;

      (e)   "MKC  Technology"  has the  meaning set out in Section 10 of the R&D
            Agreement,   but,  for  greater  certainty,  does  not  include  any
            technology that has been  independently  developed by MKC including,
            but not limited to, that  embodied in the Mitel  Networks  3050 ICP,
            and the  additional  work done to complete  the SIP capable 5055 and
            5056 IP phones from the working prototype stage reached by MNC;

      (f)   "Note" has the meaning set out in Section 2.07;

      (g)   "Price" has the meaning set out in Section 2.04

      (h)   "MNC Shares" has the meaning set out in Section 2.05.

      (i)   "Purchased Assets" has the meaning set out in Section 2.01;

1.02 Interpretation

      In this Agreement:

      (a)   all references to a designated "Article", "section", "subsection" or
            other  subdivision or to a Schedule are to the  designated  Article,
            section,  subsection  or other  subdivision  of or  Schedule to this
            Agreement;

      (b)   the words "herein", "hereof", "hereunder" and other words of similar
            import refer to this  Agreement as a whole and not to any particular
            Article, section, subsection,  Schedule or other subdivision of this
            Agreement;

      (c)   the headings are for convenience only and do not form a part of this
            Agreement  and are not  intended to  interpret,  define or limit the
            scope, extent or intent of this Agreement or any of its provisions;

      (d)   the singular of any term  includes the plural,  and vice versa;  any
            reference to the masculine,  feminine or neuter genders, as the case
            may be,  includes a reference to each of the masculine,  feminine or
            neuter  genders,  as the  case  may be,  and,  where  applicable,  a
            corporation; the word "or" is not exclusive and the word

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            "including" is not limiting whether or not non-limiting  language is
            used with reference thereto; and

      (e)   any reference to a statute  includes a reference to such statute and
            to the regulations made pursuant thereto,  as in effect from time to
            time.

1.03 Currency

      All references to currency herein are to lawful money of Canada.

                         ARTICLE 2 - SALE AND PURCHASE

2.01 Assets to be Sold and Purchased

      Upon and subject to the terms and  conditions  hereof,  MKC hereby  sells,
conveys, transfers and assigns to MNC and MNC hereby purchases and acquires from
MKC, as of the Effective Time, all of the right, title,  benefit and interest of
MKC in the MKC Technology held in the name of MKC (the "Purchased Assets").

2.02 Transfer on an "As Is" Basis

      MNC  acknowledges  and agrees with MKC that MNC is acquiring the Purchased
Assets on an "as is, where is" basis,  without any  representation  or warranty,
covenant or indemnification by MKC.

2.03 Registration of Ownership of Purchased Assets

      MKC and MNC shall execute the "short form" patent and copyright assignment
agreements attached hereto as Schedules "A" and "B" to fully effect the transfer
of rights in the patent and copyrights  identified in said schedules.  MKC shall
request  the  recordal  of  said  short  term  assignment  documentation  in all
jurisdictions  in which said patents and copyrights  exist at the Effective Time
and shall diligently and in good faith do all things required to effect recordal
of said assignments in a timely fashion.  MNC shall submit to MKC a list of such
patents and copyrights and shall  identify the relevant  jurisdictions  prior to
requesting the execution and filing of the assignments.

2.04 Price

      The price  payable to MKC for the  Purchased  Assets is  $12,526,713  (the
"Price"),  which MKC and MNC agree represents their fair market value and is the
sum of the following:


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      Class 44 Patents                                     $1,565,839
      Class 12 In-process R&D                              $10,960,874

2.05 Payment of Price

      The  Price  shall  be paid or  satisfied  by MNC  allotting,  issuing  and
delivering  to the MKC  4,555,169  common shares in the capital of MNC (the "MNC
Shares") upon execution hereof, which MNC Shares shall :

            (i)   have a stated capital in the aggregate equal to the Price;

            (ii)  be issued as fully paid and non-assessable.

2.06 Rollover Elections

      (1)   MNC and MKC  undertake to jointly  elect under Section 85 of the Act
            and any applicable similar provisions under the laws of any province
            of Canada within the time and in the form prescribed using the Price
            allocation  set out at  Section  2.04.  MNC and MKC  agree  that the
            elected  proceeds of disposition for each class of Purchased  Assets
            shall be the undepreciated capital cost of such class as that amount
            is defined under the Act.

      (2)   In the event that the Canada Customs and Revenue Agency or any other
            competent  taxing  authority at any time proposes to issue or issues
            any assessment or reassessment  on the basis that the  undepreciated
            capital  cost of any  class  of  Purchased  Assets  is less  than or
            greater than the elected  proceeds of disposition,  then to the full
            extent  permitted  under  applicable  Law,  MKC and MNC shall adjust
            amounts  set out in the  election  referred  to in  section  2.06(1)
            retroactively,  with effect on the Effective  Time,  and MKC and MNC
            shall jointly amend the election  form  accordingly  within the time
            and in the form prescribed.

2.07 Transfer Taxes and IP Registration Fees

      (1)   MNC shall be  responsible  to pay any applicable GST on the transfer
            of the Purchased Assets.

      (2)   MKC shall be  responsible  to pay all  registration,  assignment  or
            transfer fees or taxes for the Purchased Assets.

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                       ARTICLE 3 - THE CLOSING DELIVERIES

3.01 Deliveries

      MNC hereby delivers to MKC a share  certificate  dated as of the Effective
Time in favour of MKC evidencing 4,555,169 MNC Shares.

                              ARTICLE 4 - GENERAL

4.01 Benefit of the Agreement

      This  Agreement  shall  enure to the  benefit of and be  binding  upon the
respective  heirs,  executors,   administrators,  other  legal  representatives,
successors and permitted assigns of the parties hereto.

4.02 Amendments and Waivers

      No amendment to this Agreement  shall be valid or binding unless set forth
in writing and duly  executed by both of the  parties  hereto.  No waiver of any
breach of any provision of this  Agreement  shall be effective or binding unless
made in writing and signed by the party  purporting to give the same and, unless
otherwise provided, shall be limited to the specific breach waived.

4.03 Assignment

      This Agreement may not be assigned by MKC or MNC without the prior written
consent of the other.

4.04 Notices

      Any demand,  notice or other  communication to be given in connection with
this Agreement must be given in writing and shall be given by personal delivery,
by registered  mail or by  electronic  means of  communication  addressed to the
recipient as follows:

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                  To MKC:

                  Mitel Knowledge Corporation
                  555 Legget Drive, Suite 534
                  Kanata, Ontario
                  K2K 2X3,

                  Fax No.: (613) 271-9810
                  Attention: Paul Chiarelli

                  To MNC:

                  Mitel Networks Corporation
                  350 Legget Drive
                  Kanata, Ontario
                  K2K 2W7

                  Fax No.: (613) 591-2320
                  Attention: Jenifer Chilcott

or to such other address,  individual or electronic  communication number as may
be designated by notice given by either party to the other.  Any demand,  notice
or other  communication  given by personal delivery shall be conclusively deemed
to have  been  given on the day of  actual  delivery  thereof  and,  if given by
registered  mail, on the fifth Business Day following the deposit thereof in the
mail  and,  if  given by  electronic  communication,  on the day of  transmittal
thereof if given during the normal  business  hours of the  recipient and on the
Business  Day during  which such normal  business  hours next occur if not given
during such hours on any day.

4.05 Governing Law

      This  Agreement is governed by and shall be construed in  accordance  with
the laws of the Province of Ontario and the laws of Canada applicable therein.

4.06 Attornment

      For the purpose of all legal proceedings this Agreement shall be deemed to
have been performed in the Province of Ontario and the courts of the Province of
Ontario  shall have  jurisdiction  to entertain  any action  arising  under this
Agreement.  The Parent Corporation and the Subsidiary each hereby attorns to the
non-exclusive jurisdiction of the courts of the Province of Ontario.

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4.07 Counterparts

      This  Agreement  may be  executed in any number of  counterparts,  each of
which shall be deemed to be an original and all of which taken together shall be
deemed to constitute one and the same instrument.

      IN WITNESS  WHEREOF the parties have executed and delivered this Agreement
as of the date first written above.

                                         MITEL KNOWLEDGE CORPORATION

                                    Per:
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                                         MITEL NETWORKS CORPORATION

                                    Per:
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