<PAGE>

                                                                   EXHIBIT 10.12

                                 CONFIDENTIAL

--------------------------------------------------------------------------------


                                      OEM
                               PURCHASE AND SALE
                                   AGREEMENT


                                By and Between

                            NORTEL NETWORKS LIMITED

                                       &

                       CHORUM TECHNOLOGIES INCORPORATED



Confidential treatment has been requested for portions of this exhibit. The copy
filed herewith omits the information subject to the confidentiality request.
Omissions are designated as *. A complete version of this exhibit has been filed
separately with the Securities and Exchange Commission.


--------------------------------------------------------------------------------
<PAGE>

                               TABLE OF CONTENTS
                               -----------------

                                                              Page
                                                              ----

 1.  DEFINITIONS............................................     1
 2.  SCOPE..................................................     2
 3.  EXHIBITS...............................................     3
 4.  NORTEL'S PRODUCT QUALIFICATION AND ACCEPTANCE PROGRAM..     3
 5.  PRODUCT AND PROCESS CHANGES............................     4
 6.  QUALITY CONTROL AND RELIABILITY REQUIREMENTS,
     SUPPLY MANAGEMENT AND NORTEL'S AUDITING RIGHTS.........     6
 7.  ORDERING...............................................     7
 8.  DELIVERY...............................................     8
 9.  PRICES AND PAYMENTS....................................     9
10.  TITLE AND RISK OF LOSS.................................    10
11.  ACCEPTANCE OR REJECTION................................    10
12.  WARRANTY...............................................    10
13.  REPAIR PROCEDURES......................................    12
14.  REPAIR SERVICES........................................    13
15.  CONTINUING AVAILABILITY OF TECHNICAL ASSISTANCE,
     REPAIR SERVICES, MAINTENANCE, REPLACEMENT
     AND REPAIR PARTS.......................................    15
16.  TECHNICAL ASSISTANCE AND MARKETING SUPPORT.............    15
17.  DOCUMENTATION..........................................    16
18.  CONFIDENTIAL INFORMATION...............................    16
19.  INTELLECTUAL PROPERTY RIGHT INFRINGEMENT...............    17
20.  HAZARDOUS MATERIALS....................................    18
21.  INDEMNITY..............................................    18
22.  COMPLIANCE WITH LAWS...................................    19
23.  CONSEQUENTIAL DAMAGES..................................    19
24.  INSURANCE..............................................    19
25.  FORCE MAJEURE..........................................    19
26.  TERM...................................................    20
27.  TERMINATION AND CONTINUING RIGHTS......................    20
28.  NOTICES................................................    21
29.  CONTINGENT LICENSE.....................................    21
30.  GOVERNING LAW..........................................    21
31.  GENERAL................................................    21

<PAGE>

                                   EXHIBITS
                                   --------

Exhibit A -   Product Lists, Part I and Part II, Prices, Discounts, Availability
              Dates and FCA Delivery Locations
Exhibit B -   Specifications and Acceptance Program
Exhibit C -   Demand-Pull Program
Exhibit D -   Repair Services Rates, FCA Repair Locations and Technical
              Assistance Rates
Exhibit E -   Procedures for Orders utilizing EDI and TDI
Exhibit F -   Monthly Reports
Exhibit G -   Change Notification
Exhibit H -   Interim Dates
Exhibit I -   RUS Debarment Certificate
Exhibit J -   North American Free Trade Agreement - Procedures
Exhibit K -   Notices
<PAGE>

                        OEM PURCHASE AND SALE AGREEMENT

This OEM Purchase and Sale Agreement ("Agreement") entered into by and between
Nortel Networks Limited, a Canada corporation with offices located at 2800 Dixie
Road, Brampton, Ontario ("Nortel") and Chorum Technologies Incorporated, a
Delaware corporation with offices located at 1303 E. Arapaho Road, Richardson,
TX, 75081 (hereinafter referred to as  "Seller").

WITNESSETH that the Parties hereto hereby agree as follows:

1.     DEFINITIONS
       -----------

1.1    As used herein:

a)     "ARO" means after Seller's receipt of a Purchase Order or Release.

b)     "Blanket Purchase Order" means a Purchase Order which does not set forth
       a Delivery Date.

c)     "Business Day" means any day other than a Saturday, Sunday, a non-working
       day or statutory holiday observed in the jurisdiction where a right is to
       be exercised or an obligation to be executed hereunder.

d)     "Delivery Date" means the date specified in a Purchase Order or a Release
       when the Products are to be delivered to the FCA Delivery Location except
       in the event Nortel elects to take delivery of such Products at Seller's
       loading dock, in which case the Delivery Date shall be the date Nortel
       takes delivery of such Products at Seller's loading dock.

e)     "Demand-Pull Program" means Nortel's ordering process which may be
       established by mutual agreement of the Parties pursuant to Section 7
       (Ordering) and Exhibit C.

f)     "Documentation" means the documentation as described in Section 17.

g)     "EDI" means the electronic data interchange procedures established in
       Exhibit E.

h)     [*].

i)     "Exhibit" means any Exhibit listed in Section 3 hereof.

j)     "FCA Delivery Locations" means FCA delivery  at Seller's facility,
       Richardson, Texas.

k)     "FCA Repair Locations" means Seller's FCA repair location at Seller's
       facility, Richardson, Texas.

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

l)     "Free Carrier" and "FCA" have the meaning set forth in the International
       Chamber of Commerce document, "INCOTERMS 1990".

m)     "Hardware" means the hardware components of the Products and any set of
       programs in machine-executable code whether residing in fixed coded
       instructions resident in read-only memory or equivalent devices forming
       part of hardware and sometimes known as firmware or whether residing in
       any other form of memory device such as `flash memory'. "product"
       (uncapitalized "p") is not included within this definition of "Hardware."

n)     "Party" means Nortel or Seller and "Parties" means Nortel and Seller.

o)     "Prices" means the prices applicable to the Products and Repair Services
       determined in accordance with Section 9 (Prices and Payments) hereof,
       Exhibit A, Part I and Part II and Exhibit D.

p)     "Process" means a set of inter-related resources and activities which
       transform inputs into outputs; resources may include personnel, finance,
       facilities, equipment, techniques and methods.

q)     "Product" means any one of the fiber optic component products comprising
       Hardware components, as modified by Seller for Nortel and listed in the
       Product List attached hereto as Exhibit A, Part I, as such Exhibit A,
       Part I may be modified, from time to time, in accordance herewith or by
       agreement of the Parties and "Products" means some or all Products.

       Whenever the term "product" is used in this Agreement with respect to any
       Seller product, such term designates any such product listed in Exhibit
       A, Part II which has not yet been accepted by Nortel in accordance with
       Section 4 (Nortel's Product Qualification and Acceptance Process) and
       "products" means some or all products. "Product" is not included within
       this definition of "product."

r)     "Purchase Order" means any purchase order issued (by any means of
       transmission) or output of an electronic "paperless" process, initiated
       by Nortel, in respect of the Products and accepted by Seller pursuant to
       Section 7 (Ordering).

s)     "Release" means a verbal release confirmed in writing within two (2)
       Business Days, the document issued (by any means of transmission) or
       output of an electronic "paperless" process, initiated by Nortel,
       pursuant to a Blanket Purchase Order by which the Delivery Date for such
       Blanket Purchase Order or portion(s) thereof is requested.

t)     "Repair Date" means the date on which the repair of a Product is
       completed as stamped on the Products in accordance with Section 13.4.

u)     "Repair Services" means in the case of Hardware, the upgrade, the repair
       or replacement of defective Hardware as set forth in Section 14 (Repair
       Services) to be performed during and after the applicable Product
       Warranty Period.
<PAGE>

v)     "Specifications" means the technical specifications and the other
       requirements listed, described or referred to in Exhibit B, Part I,
       including acceptance test specifications, which are required to be met by
       the Products and the Documentation.

w)     "Subsidiary" means a corporation in which Nortel Networks Corporation,
       the parent company of Nortel, effectively owns or controls, and continues
       to own or control, directly or indirectly, more than fifty percent (50%)
       of the voting stock or shares.

x)     "Term" has the meaning ascribed to such term in Section 26 (Term) of this
       Agreement.

y)     "$" or "Dollars" means lawful money of the United States of America
       except as otherwise expressly set forth herein.

1.2    Any reference in this Agreement to another agreement shall mean such
       other agreement as executed by the Parties thereto and all amendments
       thereto, unless otherwise explicitly stated.

2.     SCOPE
       -----

2.1    From time to time Nortel may request Seller to sell the Products to
       Nortel and Seller agrees to sell such Products to Nortel. The sale of
       Products by Seller and the purchase of Products by Nortel shall be in
       accordance with the terms of this Agreement and Exhibits thereto.

2.2    Nortel shall have the right to request Seller to customize any Product or
       product. Upon Nortel's written request, Seller will evaluate the request
       and provide to Nortel a proposal regarding the customization of any such
       Product or product. The proposal will include, but not be limited to, the
       revised specification for the customized Product or product, the
       estimated cost of such customization, the price for the customized
       Product or product; and, an estimated completion date of Seller's
       efforts. If Nortel agrees to such proposal, Seller will so customize any
       such Product or product. Customization requirements, if any, shall be
       incorporated in the Specifications and the sale and purchase of any
       customized Product or product shall be in accordance with the terms and
       conditions of this Agreement and Exhibits thereto. At the time any
       customized Product or product is incorporated in this Agreement, Exhibit
       A, Part II and Exhibit B shall be amended to add thereto the prices and
       the availability date and the acceptance program applicable to such
       customized Product or product. In the event that the Parties are unable
       to agree on the customization of a Product or product, subject to the
       other provisions of this Agreement, Seller will continue to provide the
       Product or product without the requested customization.

       At an agreed upon charge, if requested by Nortel and agreed upon by
       Seller, the Products will incorporate Nortel's branding requirements, as
       provided by Nortel and in accordance with the Specifications to include,
       as mutually agreed on a case by case basis and without limitation,
       Nortel's name, trademark and logotype, Nortel's color, Nortel's part
       number as per Specifications, Nortel's bar-codes and/or CLEI codes,
       Nortel's technical handbook (standard gray color binder) with each
       Product, packing material with Nortel's logotype and Nortel's box bar
       coding, applicable to each shipment. In no event, however, shall Nortel
       remove any of Seller's markings, notices or
<PAGE>

       legends contained on or in the Product, product or Documentation and in
       all events Nortel shall reproduce and include any Seller markings,
       notices or legends contained on or in the Product, product or
       Documentation.

2.3    For those Products expressly stated in Exhibit A, Part I, as being
       subject to this Section 2.3, Seller hereby grants to Nortel the exclusive
       worldwide right to distribute and sell Products, directly or indirectly
       for the Term of the Agreement.

2.4    Nortel and Seller may from time to time, by mutual agreement, modify the
       Product Lists contained in Exhibit A, to add thereto other products
       offered for sale by Seller, and/or to incorporate therein enhancements or
       new features introduced in Products by Seller. Seller shall advise Nortel
       during scheduled Product marketing reviews and offer and make available
       to Nortel for incorporation in this Agreement, any new product or Product
       enhancement or new feature that Seller makes generally available. Such
       notification shall be made by Seller to Nortel within fifteen (15)
       Business Days of the Seller's internal design authorization allowing any
       such new product, enhancement or feature. Unless otherwise expressly
       stated in Exhibit A, Part I, any such new product or any Product
       enhancement or new feature will not be subject to the exclusivity granted
       to Nortel in Section 2.3 above. At the time any new product or Product
       enhancement or new feature is incorporated in this Agreement, Exhibit A,
       Part II and Exhibit B shall be amended to add thereto the prices and the
       availability date and the acceptance program applicable to such new
       product or Product enhancement or new feature.

2.5    Reserved.

2.6    Seller accepts and acknowledges that Nortel may request it to sell
       Products to Nortel Companies. Upon the agreement of Seller and the
       agreement of the Nortel Company to the obligations and duties imposed by
       this Agreement, Seller will grant the Nortel Company the right to place
       Purchase Orders together with the obligations and rights which accrue in
       respect of the Products or in respect of the ordering or delivery of such
       Products in accordance with this Agreement. For the purposes of giving
       effect to the above, where a Nortel Company purchases Products pursuant
       to this Agreement, where the context so admits, references to Nortel
       shall be deemed to be to the relevant Nortel Company which is ordering
       and/or purchasing Products in accordance with the terms of this
       Agreement. Notwithstanding the foregoing, in no event shall Seller be
       required to accept any Purchase Order issued by Nortel Companies in
       excess of factory capacity or the Forecast provided by Nortel; neither
       shall Seller be liable to Nortel for the failure to (a) accept any
       Purchase Order placed by Nortel Companies; or, (b) agree to extend this
       Agreement to any Nortel Companies. In no event shall Seller be required
       to deal with any Nortel Companies. For the purpose of this Agreement,
       "Nortel Company" shall mean individually or collectively: (i) a
       Manufacturing Licensee (i.e. a third party which enters into an agreement
       with a Nortel Company to (1) manufacture in modified or unmodified form,
       a Nortel product incorporating the Product, and (2) lease, sell,
       sublicense or otherwise distribute (directly or indirectly) through
       distributors such Nortel product under Nortel's or the Manufacturing
       Licensee's own brand name) and agreed upon by Seller (such agreement not
       to be unreasonably withheld); and/or (ii) any other legal entity
       (including, but not limited to a joint venture, which is a cooperative
       enterprise formed between a
<PAGE>

       Nortel Company and one or more other autonomous entities to address more
       effectively certain mutual business interests and opportunities) which
       qualifies as a Subsidiary.

3.     EXHIBITS
       --------

3.1    The following Exhibits, attached hereto, are an integral part of this
       Agreement and are incorporated herein by reference:

       Exhibit A -   Product Lists, Part I and Part II, Prices, Discounts,
                     Availability Dates and FCA Delivery Locations
       Exhibit B -   Specifications and Acceptance Program
       Exhibit C -   Demand-Pull Program
       Exhibit D -   Repair Services Rates, FCA Repair Locations and Technical
                     Assistance Rates
       Exhibit E -   Procedures for Orders utilizing EDI and TDI
       Exhibit F -   Monthly Reports
       Exhibit G -   Change Notification
       Exhibit H -   Interim Dates
       Exhibit I -   RUS Debarment Certificate
       Exhibit J -   North America Free Trade Agreements - Procedures
       Exhibit K -   Notices

3.2    Any amendment to any Exhibit shall be in the form of a revised Exhibit
       duly dated and signed by authorized representatives of the Parties.

4.     NORTEL'S PRODUCT QUALIFICATION AND ACCEPTANCE PROGRAM
       -----------------------------------------------------

4.1    Seller undertakes to supply Products which comply with the
       Specifications. Except as otherwise set forth herein, prior to being
       purchased by Nortel, the products listed in Exhibit A, Part II will
       undergo a program of evaluation, qualification and acceptance by Nortel
       ("Acceptance Program") to verify their compliance with the
       Specifications. Products listed in Exhibit A, Part I have been accepted
       by Nortel in accordance with this Section 4. The Acceptance Program will
       be conducted in accordance with Exhibit B, Part II.

4.2    It is acknowledged by Seller that circumstances may arise where Nortel
       will desire to purchase one or more products as are listed in Exhibit A,
       Part II, prior to acceptance thereof in accordance with this Section 4.
       Such circumstances will be examined in good faith by the Parties on a
       case-by-case basis. In the event Seller accepts to sell any one of the
       products, Nortel will issue Purchase Order(s) covering same.

4.3    Acceptance by Nortel of the products will take place upon successful
       completion of Nortel's Acceptance Program. Nortel will notify Seller in
       writing of its acceptance of the products within three (3) Business Days
       from successful completion of its Acceptance Program.

4.4    In the event that in the course of the carrying out of the Acceptance
       Program, Nortel determines that the products fail to comply with the
       Specifications, Nortel will promptly notify Seller in
<PAGE>

       writing of such failure, with reasonable detail, and upon receipt of such
       notice, Seller will, at its expense, take prompt and effective action to
       correct the notified deficiencies by the applicable Acceptance Date, as
       such term is hereafter defined. Product acceptance dates shall be agreed
       upon by the Parties on a case-by-case basis, any such date to be, in any
       event, no later than [*] after the date specified in Exhibit A, Part II
       for each product (herein referred to as "Acceptance Date"), or extensions
       thereof, if any, granted in writing by Nortel. In such case, acceptance
       of the products will take place upon verification by Nortel that the
       notified deficiencies have been corrected, and accepted products shall
       become Products hereunder and be deemed to be included in Exhibit A,
       Part I.

4.5    In the event that acceptance of the products does not take place on or
       before the Acceptance Date or extensions thereof, if any, granted in
       writing by Nortel, or in the event Nortel, acting reasonably, does not
       expect that acceptance will take place on the Acceptance Date or
       extensions thereof, if any, granted in writing by Nortel, Nortel may, in
       addition to any other remedies hereunder, at law or in equity, recover
       [*]. In addition Nortel may, upon notice to Seller to that effect,
       request that a design review be held between Seller's and Nortel's
       engineers in order to determine how far away the products actually are
       from acceptance.

4.6    In the event Seller has accepted Nortel's Purchase Order(s) for products
       pursuant to Section 4.2 hereof, Nortel may, in addition to its rights
       under Section 4.5 hereof, request that Seller provide, and in such event,
       Seller will provide as a temporary solution, functionally equivalent
       equipment acceptable to Nortel's customer(s). Once the products have
       passed acceptance, Seller shall, at its own cost, replace the
       functionally equivalent equipment with the Products, and shall invoice
       Nortel for the price of Products only, once the Products have been
       delivered to Nortel's customer(s). Nortel shall not be responsible for
       the cost of the equipment sent as an alternate and temporary solution.

4.7    Seller has identified and will continue to identify to Nortel any sole
       source/critical components incorporated into the Products. For purposes
       of this Agreement, "critical components" means those parts of the
       Products for which there is no other readily identifiable source.

4.8    Acceptance of the Products by Nortel under this Section 4 shall not
       relieve Seller from its obligations to manufacture, deliver, repair and
       support the Products in accordance with this Agreement.

5.     PRODUCT AND PROCESS CHANGES
       ---------------------------

5.1    Seller shall notify Nortel in writing of all proposed modifications and
       changes that affect form, fit, function, performance or Price (herein
       "Change(s)") to the Products and/or Processes. Such notification shall be
       made by Seller to Nortel within [*] of Seller's internal design
       authorization allowing any such Change except in the cases contemplated
       in Section 5.6, in which case Seller shall promptly so notify Nortel and
       initiate immediate action to correct the situation. The Changes which
       require that a notice be forwarded to Nortel shall be any proposed

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

       Change to the Products in accordance with the classifications described
       in GR-209-CORE incorporated by reference ( "GR-209") unless otherwise
       expressly set forth in this Section 5. All Changes proposed outside the
       spectrum of GR-209 shall be classified as "O". The interpretation of GR-
       209 shall be decided on a per product basis in agreement between Seller
       and Nortel prior to acceptance of a given PO or addition of a product to
       Product List in Exhibit A. Seller's Change notifications (herein "Change
       Notifications") shall be in the form and content of Exhibit G.

*  See Exhibit H

5.2    Seller's written Change Notifications shall be numbered in a single
       sequential numbering scheme and shall include the information specified
       in GR-209. In addition, a detailed description of the Change, the
       consequences if the Change is not implemented and the planned
       implementation date of the Change shall be included in the Change
       Notification.

5.3    Nortel reserves the right to request reasonable test data associated with
       any Product Changes. Furthermore, in the event Nortel determines it is
       necessary to verify the Change prior to acceptance, Seller shall supply,
       on loan and without charge, a mutually agreed upon quantity of Products
       for such verification, or offer some other alternative arrangement,
       satisfactory to Nortel, for such verification.

5.4    If Nortel disagrees with any classification issued by Seller, Seller
       shall present evidence in writing, within a period of [*] from Nortel's
       request therefore, that such a classification is justified. If Nortel
       still disagrees with the justification, within [*] from its receipt of
       Seller's written justification of the classification, Nortel shall
       present evidence in writing that Nortel's disagreement is justified and
       made in good faith and based on Nortel's product implementation
       requirements. Thereafter, the Parties shall negotiate in good faith until
       a final resolution is mutually agreed upon by the Parties within [*] from
       the date of Seller's Change Notification. In the event that [*] after the
       date of Seller's Change Notification, the Parties still disagree on the
       Change classification, Nortel's reasonable and substantiated
       determination shall prevail and be final.

5.5    Seller shall not implement a Change such as those contemplated above
       without the prior written consent of Nortel, provided such consent is not
       unreasonably withheld. Should Nortel fail to respond within a period of
       [*] from the date it has received a notice forwarded by Seller under this
       Section 5, then Seller shall have the right to implement such Change and
       Nortel forfeits all rights to object to such Change.

5.6    In addition to Seller's warranty obligations contained in Section 12
       (Warranty) and without diminishing Seller's obligations under this
       Section 5 and Sections 6 (Quality Control and Reliability Requirements,
       Supply Management and Nortel's Auditing Rights) and 14 (Repair Services)
       but only on a customer by customer basis and only for as long as Nortel
       is similarly obligated to such customer with regard to Class A or AC
       Changes, in the event that an intrinsic design or manufacturing defect of
       the Product(s), causes an inoperative, hazardous or unsatisfactory
       condition of a nature as to require the introduction in the Product(s) of
       a Class A or AC Change, as described in GR-209, Seller shall, as
       expeditiously as possible, at its expense, generate a Class A or AC
       Change, as applicable, to eliminate the defect, and supply such Change,

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

       at no charge, for installation by Nortel at reasonable costs, at Seller's
       expense, in all defective units of the Product(s), both installed and
       stocked, in accordance with a retrofit program negotiated by Nortel with
       its customers. A retrofit program is a program that allows Nortel to
       install the Change in all of Nortel's stockrooms and customer locations
       within a period not to exceed [*] from the date such inoperative,
       hazardous or unsatisfactory condition first occurs. In the course of
       negotiations of the retrofit program with its customers, Nortel shall
       consult closely with Seller with a view to endeavor to achieve the
       twofold objective of customers' satisfaction and minimization of retrofit
       costs to Seller.

       Seller shall provide, at its expense, seed stock units to support a
       retrofit project completion within said [*] in quantities determined in
       accordance with the following formulae: The [*] period begins when all
       the details of the retrofit program are determined by Nortel.

       Seed Stock Units = Material Cycle Time (Weeks) x Repair and Return Rate

       Repair and Return Rate =         Number of units to be retrofitted
                                        ---------------------------------------
                                Change Completion Date - Implementation Date

5.7    Nortel shall provide to Seller Nortel's Product Engineering Code, the
       release number of the Product and the CLEI code of the Product, if
       required, for each Product Change under this Section 5. At Nortel's
       request, this information shall be placed on the Products by Seller in
       accordance with the Specifications.

5.8    From acceptance of the Products by Nortel in accordance with Section 4
       (Nortel's Product Qualification and Acceptance Process), Seller shall
       provide Nortel with a field baseline report which will include: part
       number, Current Revision Level, New Revision Level, Reason for Change,
       Parts affected by Change, Old and New Revision of PCB, if applicable.
       This report will be updated whenever a Change is generated by Seller
       which affects form, fit, function, performance or Price of the Products.
       Seller will use its best efforts to produce these updates within seven
       (7) Business Days* of each Change date.

5.9    Throughout the Term, Seller shall requalify the Products once every [*]
       period in accordance with Bellcore Standard TR-NWT-000418, Issue 2
       (Draft 3) September 1992.

5.10   Change notices relating to Product Changes should be sent to Nortel's
       System Engineering department and Change notices relating to Process
       Changes should be sent to Nortel's Quality Department. Seller's Quality
       Department shall be responsible for the obligations described in this
       Section 5.

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

6.     QUALITY CONTROL AND RELIABILITY REQUIREMENTS, SUPPLY MANAGEMENT AND
       -------------------------------------------------------------------
       NORTEL'S AUDITING RIGHTS
       ------------------------

6.1    ISO 9001 and 9002 Certification
       -------------------------------

6.1.1  Seller will use commercially reasonable efforts to obtain ISO 9002
       certification by [*]. After such certification is received, Seller
       undertakes to maintain ISO 9002 certification in effect throughout the
       Term including in respect of Seller's quality control systems and
       Seller's failure to maintain ISO 9002 certification shall constitute a
       material breach by Seller of its obligations hereunder. Seller expects to
       obtain ISO 9001 certification by [*]. After ISO 9001 certification is
       received, Seller agrees to maintain such certification in the same manner
       as set forth above for ISO 9002 certification.

6.1.2  In the event Seller receives any notice of non-conformance to ISO from
       the ISO registrars, Seller shall immediately advise Nortel and forthwith
       provide Nortel with (i) the list and details of the non-conformance and
       (ii) the detailed plan submitted to the ISO registrars including
       timelines and goals to achieve compliance with the applicable ISO
       certification.

6.2    Quality Control and Reliability Requirements
       --------------------------------------------

6.2.1  The Nortel quality and reliability target metrics shall be set out in the
       Specifications, such metrics to include, without limitation, Mean Time
       Between Failure ("MTBF"), Return Rate ("RR") and Seller Product Quality
       Level ("SPQL"). In the event Nortel proposes any changes or additions to
       such quality and reliability target metrics, Seller shall not
       unreasonably refuse to agree or delay compliance with such changes.

6.2.2  Products furnished hereunder by Seller shall be tested and inspected by
       Seller prior to shipment in accordance with testing and inspection
       procedures contained in the Specifications. Seller agrees to perform the
       quality control functions set forth in the Specifications. Detailed
       inspection records are to be maintained by Seller and made available to
       Nortel upon request.

6.2.3  Seller shall provide Nortel with a monthly report covering the items
       shown in Exhibit F and any other items reasonably required by Nortel in a
       format acceptable to Nortel.

6.2.4  Seller shall within [*] of becoming aware of such event, report to Nortel
       by Technical Bulletin any potential, suspected or actual (i) defect in
       design and/or manufacturing of the Products, (ii) malfunction of the
       Products or of products similar to the Products, (iii) failure of the
       Products to conform to the Specifications or (iv) uses of the Products in
       combination with other product(s) or services which cause or have the
       potential of causing disruption in the services provided by end-users
       using the Products.

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

6.3    Supply Management
       -----------------

6.3.1  Seller's procurement Process must cover all reasonable activities related
       to the purchase of components and materials used in the finished Product
       including the selection of Seller approved suppliers and the acceptance
       by Seller of the material. Seller shall ensure through its procurement
       Process that only Seller qualified components and materials from Seller
       approved suppliers are used in the manufacture of Product at Seller's
       manufacturing facilities.

6.3.2  Seller's supply management Processes, excluding any specific supplier
       information, are subject to reasonable inspection by Nortel to assess
       their effectiveness and ensure corrective and preventive actions are
       taken internally by Seller. Nortel's inspection of the Processes may be
       held, upon reasonable prior notice, within [*] of evidence of receiving
       Products from Seller that do not comply with the particular
       Specification.

6.3.3  Where Nortel reasonably determines that certain components used in
       Products contain potential problem areas, it shall notify Seller in
       writing, and the Parties shall discuss the matter with a view to
       confirming a problem area exists, and then mutually agreeing to ways to
       resolve such problem areas.

6.4    Nortel's Inspection Rights
       --------------------------

6.4.1  Upon advance notice to Seller and only without unduly interfering with
       Seller's normal day-to-day operations, Nortel may inspect or test, at all
       reasonable times and at Seller's locations, any Products covered by this
       Agreement. Seller shall provide such reasonable assistance as is
       reasonably required to allow Nortel to perform a full range of quality
       assurance functions without unduly interfering with Seller's normal day-
       to-day operations. Seller shall provide such reasonable assistance at no
       additional charge; provided, however, that in the event Seller is
       required to purchase any goods or services to accommodate Nortel's
       request, Nortel shall reimburse Seller for the expenses incurred by
       Seller. Inspection of Products may be performed in whole or in part prior
       to final assembly and/or completion of manufacturing or repair Processes.

6.4.2  In addition to, and without restricting, Nortel's auditing and inspection
       rights described in this Section 6, Nortel shall have the right to visit
       Seller's manufacturing location(s) for the purpose of inspecting any of
       the Processes, upon [*] written notice and only without unduly
       interfering with Seller's normal day to day operations. Nortel shall
       request inspection no more frequently than required by good commercial
       practices.

6.4.3  Nortel shall keep Seller informed as to any problems encountered with the
       Products and Processes and to communicate promptly to Seller any and all
       modifications or improvements to the Products and Processes suggested by
       any customer, employee or agent, as Nortel considers appropriate.

6.4.4  Any exercise of Nortel's right to inspect Products, Processes and
       Seller's manufacturing locations as set forth in this Section 6 and
       Section 11 (Acceptance or Rejection) shall not constitute, or be
       construed as acceptance of the Products and Processes by Nortel or
       relieving Seller from its

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       obligations to furnish all Products in strict compliance with this
       Agreement, including the Specifications, and the applicable Blanket
       Purchase Order, Release or Purchase Order.

7.     ORDERING
       --------

7.1    Products will be purchased, upon mutual agreement of the Parties, through
       Blanket Purchase Orders and Releases under the Demand-Pull Program, in
       accordance with Exhibit C, or, absent such Demand-Pull Program, through
       Purchase Orders with a schedule of delivery, which may be issued by
       Nortel, from time to time, in accordance with this Agreement. Seller
       agrees to be compliant with the Demand-Pull Program no later than [*].

7.2    Notwithstanding that a Blanket Purchase Order, a Release or a Purchase
       Order issued in respect of Products does not refer to this Agreement, any
       such Blanket Purchase Order, Release or Purchase Order issued by Nortel
       during the Term shall be deemed to have been issued pursuant to this
       Agreement and shall be deemed to incorporate and be governed solely by
       the terms and conditions set forth in this Agreement unless the Parties
       expressly agree in writing to the contrary. Any printed terms and
       conditions contained in any Blanket Purchase Order, Release or Purchase
       Order or in any Seller's acknowledgment, invoice or other documentation
       shall be deemed deleted and of no force or effect. Any additional typed
       and/or written terms and conditions contained in any Purchase Order or
       Release and any Seller's acknowledgment, invoice or other documentation
       shall be for administrative purposes only, i.e. to identify the types and
       quantities of Products to be supplied, line item Prices and total Price,
       delivery schedule, and other similar ordering data, all in accordance
       with the provisions of this Agreement.

7.3    Nortel shall not be obligated to purchase any quantities of Products
       hereunder, except and only to the extent required in order to satisfy its
       obligations to purchase Products pursuant to (a) the Demand-Pull Program,
       if any, as expressly set forth in Exhibit C; or (b) Section 8.5 below.

7.4    Seller undertakes to accept any Blanket Purchase Orders and Releases or
       Purchase Orders issued hereunder by Nortel and Nortel Companies, provided
       that such Blanket Purchase Orders and Releases or Purchase Orders are
       consistent with this Agreement. Seller shall acknowledge receipt of each
       Blanket Purchase Order, Release or Purchase Order within [*] ARO. For the
       avoidance of doubt, Seller may reject any Blanket Purchase Order,
       Releases or Purchase Orders which (i) is not consistent with the terms of
       this Agreement; (ii) is issued under the Demand-Pull Program and exceeds
       the quantity contained in the Forecast provided to Seller; or (iii) is
       not issued under the Demand-Pull Program and Seller, in its sole
       judgment, does not believe it can provide the quantity requested by the
       requested delivery date.

7.5    Any change to the original Purchase Order or Release initiated by Nortel
       after Seller's acknowledgment and any resulting adjustments to Prices,
       schedule and/or other requirements of the Purchase Order or Release shall
       be negotiated and mutually agreed upon and subsequently detailed in a
       written change to the Purchase Order or Release ("Change Order"),
       referencing the original Purchase Order or Release and executed by
       authorized representatives of Nortel and Seller. [*].

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7.6    The Blanket Purchase Orders, Releases, or Purchase Orders shall:

       a)  reference the number of Nortel's Blanket Purchase Order, Release or
           Purchase Order issued for the Products;
       b)  include a signature of an authorized employee of Nortel (to be
           provided by Nortel);
       c)  have the correct Product and options description (including item
           numbers and part numbers if shown for that item in the Product list);
       d)  have the correct Price in accordance with Exhibit A of this Agreement
           or any amendments hereto;
       e)  specify the exact quantity of Products to be delivered;
       f)  provide tax status for each FCA Delivery Location including the
           exemption certificate number if tax exempt;
       g)  have firm delivery schedules and a firm Delivery Date (where
           applicable) for each shipment;
       h)  specify the FCA Delivery Location and the Nortel location where the
           invoice shall be rendered for payment;
       i)  specify the method of shipment including the names of carrier and
           broker, if applicable; and
       j)  specify special shipping and transportation instructions, if any.

8.     DELIVERY
       --------

8.1    Products shall be delivered as follows:

       a)  Products ordered pursuant to the Demand-Pull Program shall be
           delivered by Seller FCA Delivery Location set forth in the Release
           within a delivery lead time not to exceed [*] from Nortel's
           Release(s).

       b)  Products not ordered pursuant to the Demand-Pull Program shall be
           delivered by Seller FCA Delivery Location set forth in the Purchase
           Order, within a delivery lead time as mutually agreed by the Parties,
           but not to exceed; (i) [*], if forecasted in the manner mutually
           agreed upon by the Parties, or (ii) [*] ARO, if not forecasted.

       No partial shipment shall be made without prior written approval from
       Nortel.

8.2    Seller shall package the Products in accordance with the packing and
       external marking practices listed in Schedule B, Part III and the
       Specifications.

8.3    Seller shall mark each Product listed in Exhibit A in accordance with the
       Specifications and as set forth in Exhibit B, Part III.

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8.4    In the event that Seller fails to deliver Products by the Delivery Date
       or extension thereof granted by Nortel, if any, and provided that such
       failure is not due to a Force Majeure event (Section 25 below), Nortel
       may, as its sole and exclusive remedy, cancel, without charge or
       liability, the affected Purchase Order and/or Release or applicable
       portion thereof. Seller shall promptly advise Nortel of any anticipated
       delay in meeting the Delivery Date specified in any Purchase Order or
       Release and shall cooperate with Nortel in the implementation by Seller
       of any appropriate action or workaround plans. Without limiting the
       generality of the foregoing or otherwise affecting Nortel's rights, in
       the event a Nortel customer cancels one or more orders for Products as a
       result of Seller's delay in the delivery of Products of more than [*] and
       provided that such delay is not due to a Force Majeure event (Section 25
       below), Nortel shall have the right to cancel, without charge or
       liability, the Purchase Order and/or Release issued to Seller in respect
       of Nortel's customer cancelled order(s).

8.5    Prior to [*] Nortel agrees to purchase at least [*] units of Products
       from Seller as set forth in Appendix A ("2000 Commitment").

       In addition, in the event that Seller's Product delivery, pricing and
       ability to ramp-up to Nortel's demand meet or exceed Nortel's
       expectations, then Nortel may purchase an additional mutually agreeable
       quantity of Products from Seller during the [*] of the Agreement.

8.5.1  Beginning on [*], for each calendar year of the Term, Nortel agrees to
       issue Purchase Orders to Seller as set forth in Appendix A ("Annual
       Commitment") on the following basis:

       a)  where Seller has complied with the performance requirements set out
           in Section 8.5 to the reasonable satisfaction of Nortel during the
           preceding [*] period, a Nortel Annual Commitment shall remain overall
           at the said same level;

       b)  where Seller has reasonably exceeded the performance requirements set
           out in Section 8.5, to the reasonable satisfaction of Nortel during
           the preceding [*] period, and subject to Nortel's other legal
           obligations and commitments, Nortel shall in good faith use
           reasonable commercial efforts to increase the percentage of business
           in a Nortel Annual Commitment to match the level of the exceeded
           performance by Seller, provided that Nortel makes no firm commitment
           to effect such increase;

       c)  where Seller has failed to meet the performance requirements set out
           in Section 8.5, to the reasonable satisfaction of Nortel, during the
           preceding [*] period, then the percentage of business in a Nortel
           Annual Commitment may be decreased by an amount equal to [*] per
           calendar quarter for each Product type that had [*] or more Delivery
           Defaults in such quarter. Subject to Section 9.4 and 9.5, Nortel
           acknowledges and understands that the Prices charged by Seller may
           increase.

       In the event that Seller is unable to deliver sufficient quantities of
       Products in order to satisfy a Nortel Commitment as set forth above due
       to no fault of Nortel, the Parties agree that Nortel shall be relieved of
       any obligation to fulfil the remainder of the applicable Commitment.

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<PAGE>

8.5.2  [*].

8.5.3  Nortel's Annual Commitments may decrease (and any such decrease may
       subsequently be reversed as provided for herein) in accordance with the
       following:

       "Delayed Delivery" shall be any instance where Seller fails to make a
       shipment that a) is in compliance with the quantity of Products in a
       Release and the delivery date of such Products in accordance with Section
       3.4 of Exhibit C, for Products supplied pursuant to the Demand-Pull
       Program, or b) as per the mutually agreed upon delivery date with respect
       to Products ordered under a Purchase Order.

       "Default Period" shall be any calendar week where Seller has made a
       Delayed Delivery.

       "Delivery Default" will be deemed to occur if there are [*].

       Upon the occurrence of a Delivery Default, Nortel may, upon written
       notice to Seller, reduce by up to [*] Nortel's Annual Commitment for the
       particular Product for that calendar quarter.

       Upon the occurrence of a second Delivery Default for the same particular
       Product within the same calendar quarter, Nortel may, upon written notice
       to Seller, reduce by up to an additional [*] Nortel's Annual Commitment
       for the particular Product for that calendar quarter.

       Upon the occurrence of a third Delivery Default for the same particular
       Product within the same calendar quarter, Nortel may, upon written notice
       to Seller, reduce by up to an additional [*] Nortel's Annual Commitment
       for the particular Product for that calendar quarter.

       In addition, and notwithstanding the terms of this Section 8.5, Seller
       herein recognizes Nortel's need to respond to increases in demand for the
       Products, and to the extent that Seller cannot meet such increases in
       demand, it is understood that Nortel may seek, at its sole discretion to
       have such increased demand fulfilled by another supplier.

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       If, at anytime within [*] from the date of written notice to Seller
       reducing a Nortel Annual Commitment pursuant to the foregoing provisions,
       there are [*], then such reduction to Nortel's Annual Commitment for that
       particular Product will be reversed and returned to the original level of
       Nortel's Purchase Commitment for that particular Product prior to such
       reduction; provided, however, that if Nortel actually purchases and
       receives delivery of the total quantity by which Seller is in default
       under the Delivery Default of that particular Product from an alternative
       vendor for that particular Product covered by that Delivery Default, and
       if such alternative vendor makes a permanent investment in capital
       equipment, personnel and supply chain commitments in order to supply such
       Products, then Nortel will have no obligation to make up the value of the
       business Seller has lost due to such Delivery Default.

8.5.4  The Parties agree that Seller is currently operating at [*], at which
       time Seller agrees to provide the following flex ramp-up.

       In the event Nortel provides at least [*] written notice to Seller,
       Seller shall use commercially reasonable efforts to deliver up to an
       additional [*] of the quantity Forecasted after such [*]. Additionally,
       in the event Nortel provides at least [*] written notice to Seller,
       Seller will use commercially reasonable efforts to deliver up to an
       additional [*] of the quantity Forecasted after [*]. Notwithstanding
       anything to the contrary set forth in this paragraph above, Seller agrees
       to use commercially reasonable efforts, but shall have no obligation to
       increase capacity by more than [*] of the Forecasted quantity during any
       [*].

8.5.5  The Parties may mutually agree to hold operational reviews at mutually
       agreed upon times and places during the Term of the Agreement.

8.6    Nortel may at any time, for its convenience and without cause, reschedule
       the Delivery Date of ordered Products, provided such rescheduled Delivery
       Date shall not exceed [*] from the date the Products were originally
       scheduled to be delivered.

8.7    Nortel may at any time for its convenience and without cause, cancel, in
       whole or in part, any Purchase Order placed hereunder for Products
       subject to the payment of a cancellation fee based on the total Price of
       the cancelled Products in accordance with the following:

       (a)   finished Products = [*]
       (b)   Products in progress:
             Cancellation less than [*] but at least [*] before the
             Delivery Date = [*]
             Cancellation less than [*] but at least [*] before the
             Delivery Date = [*]
             Cancellation less than [*] before the Delivery Date = [*]

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9.     PRICES AND PAYMENTS
       -------------------

9.1    Except as specifically provided herein, all charges incurred by Seller in
       performing its obligations hereunder shall be paid by Seller and shall
       not be subject to reimbursement by Nortel.

9.2    Prices shall be firm throughout the Term [*] or an increased Nortel
       volume discount; unless changes to form, fit or function are implemented
       in any product at the request of Nortel. If said changes are requested by
       Nortel, Seller has to right to renegotiate price of affected product [*].

9.3    Prices are: (a) FCA Seller's Richardson, TX plant; (b) stated and payable
       in US currency; (c) include packing; and (d) exclude all applicable
       federal, state and local taxes and import duties or custom charges.

9.4    Seller agrees that the Prices charged to Nortel for Products and Repair
       Services supplied hereunder are and will continue to be [*], at a
       particular time, for the same Products purchased in similar quantities
       and under terms and conditions substantially similar to those contained
       in this Agreement, including, without limitation, any purchase
       commitments. For comparison purposes, Seller shall aggregate purchases of
       Products by all Nortel Companies.

9.5    Seller further agrees that the Prices charged to Nortel for Products and
       Repair Services supplied hereunder are and will continue to be [*]
       charged by Seller, at a particular time, [*] has entered into an OEM
       agreement (or similar contractual arrangement), for [*] Products
       purchased [*] to those contained in this Agreement, including without
       limitation, any purchase commitments. For comparison purposes, Seller
       shall aggregate purchases of Products by all Nortel Companies

9.6    Seller shall promptly notify and extend to Nortel [*] made by Seller in
       its published list prices and [*] shall apply to Blanket Purchase Orders,
       Releases and Purchase Orders received by Seller on or after the effective
       date of the price reduction. Any price decreases will be immediately
       applied to any Blanket Purchase Orders, Releases or Purchase Orders
       received and acknowledged but not delivered by Seller.

9.7    In an effort to provide Nortel the opportunity to competitively and
       profitably offer Products in high volume applications, [*].

9.8    Payment shall be due to Seller from Nortel [*] following the receipt by
       Nortel of an invoice for the Products, which invoice shall be delivered
       to Nortel no earlier than the Delivery Date of the Products.

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9.9    Invoices for Products delivered hereunder and for any other amounts,
       which may be payable hereunder, shall be forwarded directly to the
       following address (unless Nortel designates, in writing, another
       address):

       NORTEL NETWORKS INC.

       P.O. Box 90510
       Nashville, TN 37208-0510
       U.S.A.

       Attention:  Accounts Payable Dept.

10.    TITLE AND RISK OF LOSS
       ----------------------

10.1   Title to the Products (excluding Software) and risk of loss of and damage
       to the Products will pass to Nortel [*] provided that under Section
       12.1.1 (Warranty), 13.2 and 13.7 (Repair Procedures), risk of loss of or
       damage to the replacement Products will pass to Nortel upon the delivery
       thereof at a Nortel designated destination.

11.    ACCEPTANCE OR REJECTION
       -----------------------

11.1   Nortel reserves the right to accept or reject, in accordance with Section
       11.2 below, Products ordered hereunder after the delivery of such
       Products to Nortel's facility or, as the case may be, to a Nortel
       Customer's site. Products shall be deemed accepted by Nortel unless
       Nortel notifies Seller, in writing, that such Products are rejected and
       provides the reasons for such rejection within [*] after Nortel's receipt
       thereof at its facilities or, when the Products are received at a Nortel
       customer's site, as the case may be, upon completion of installation and
       testing of the Products or [*] after such receipt of the Products at such
       customer site, whichever event occurs first.

11.2   If any Products are found not to be in substantial conformance with the
       Specifications, and/or fail to meet any of the acceptance criteria
       specified in the applicable Specifications, and/or in the event an
       excessive failure rate (as defined in the Specifications) is observed by
       Nortel with respect to Products contained in a lot/shipment, Nortel shall
       have the right, notwithstanding the warranty provisions contained in this
       Agreement, to reject the same. Nortel shall promptly return to Seller the
       rejected Products and Seller will repair or replace the rejected Products
       within [*] of receipt of the rejected Products. Return shipment of the
       rejected Products will be at Seller's risk and expense (including
       shipping charges). Any notice of rejection issued by Nortel under this
       Section 11.2 will include a reasonable description of the deficiencies.

11.3   Payment or acceptance by Nortel shall not be deemed to constitute a
       waiver of the rights which Nortel may have resulting from Seller's
       delivery of faulty or defective Products.

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12.    WARRANTY
       --------

12.1   Seller warrants that:

       a)    Product shall, at the Delivery Date, be new and free and
             clear of all security interest or other lien and other encumbrance;

       b)    for a period of [*] from the Delivery Date or, [*] from the
             manufacturing date stamped on the Products, whichever period
             expires last (such period being hereinafter referred to as the
             "Product Warranty Period"), the Products shall be free from defects
             in materials and workmanship and shall conform to and operate in
             accordance with the Specifications;

       c)    with the exception of any notice which may be provided by Seller
             pursuant to Section 20 (Hazardous Materials), the Products
             furnished by Seller, and the components thereof, are not
             considered, under the laws of the U.S. or Canada, toxic or
             hazardous to persons or the environment;

       d)    no license or other agreement is or will be violated by the terms
             and conditions of this Agreement;

       e)    without limiting the generality of the foregoing provisions, that
             it has the authority to enter into this Agreement and has obtained
             all rights and waivers necessary to sell Products to Nortel and to
             grant the rights granted hereunder.

       f)    that the Products and the exercise of the rights granted in this
             Agreement do not infringe any third-party patent, copyright,
             trademark, trade secret or other intellectual property right.

12.1.1 The warranty provisions contained in Sections 12.1(c), (d), (e) and (f)
       shall apply during and after the Product Warranty Period and shall
       survive inspection, acceptance and payment

12.2   The warranty in Section 12.1(b) above does not apply to items normally
       consumed in operation, such as lamps and fuses and to any defect which
       has been caused by Nortel or arises from mishandling, misuse, neglect or
       improper testing or repair or modification or repair by any party other
       than Seller. Any failure of the Hardware determined by Seller to not have
       resulted from a defect covered by the warranty in Section 12.1(b) above,
       will, at Nortel's option and expense, be returned to Nortel, without the
       performance of Repair Services or repaired, in accordance with Section 14
       (Repair Services) and returned to Nortel.

       Subject to the paragraph above, as Nortel's sole and exclusive remedy and
       Seller's sole and exclusive liability for breach of the warranty in
       Section 12.1(b) above, Seller shall, at its expense, during the Product
       Warranty Period, provide Repair Services in accordance with Section 14
       (Repair Services) in respect of Hardware which have failed to conform to
       the warranty listed in Sections 12.1(b) above as confirmed by Seller's
       testing and inspection of the Hardware after return of the Hardware by
       Nortel. Hardware repairs or replacements effected during the Product
       Warranty Period shall be warranted, as above provided, for the remainder
       of the Product

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       Warranty Period or for [*] from the Repair Date, whichever is longer.
       Hardware repairs or replacements effected after expiry of the Product
       Warranty Period shall be warranted, as above provided, for a period of
       [*] from the Repair Date stenciled or otherwise identified in accordance
       with Section 13.4 (Repair Procedures). All transportation and other
       expenses arising from shipping the non-conforming Products to Seller
       shall be paid by Nortel, and the repaired or replacement Products from
       Seller to Nortel shall be paid by Seller.

12.3   NORTEL'S SOLE AND EXCLUSIVE REMEDY AND SELLER'S SOLE AND EXCLUSIVE
       LIABILITY FOR ANY BREACH OF THE WARRANTIES SET FORTH IN SECTIONS 12.1(B),
       (D), (E) OR (F) ABOVE OR FOR PRODUCT DEFECTS SHALL BE ITS RIGHTS AS SET
       FORTH IN THIS SECTION 12.

12.4   NORTEL'S SOLE AND EXCLUSIVE REMEDIES, AND SELLER'S SOLE AND EXCLUSIVE
       LIABILITY, FOR ANY BREACH OF THE WARRANTIES CONTAINED IN SECTIONS 12.1(D)
       OR 12.1(E) OR 12.1(F) ABOVE SHALL BE (A) TERMINATION OF THIS AGREEMENT;
       AND/OR (B) THE INFRINGEMENT INDEMNITY PROVIDED IN SECTION 19 BELOW.

       EXCEPT FOR THE EXPRESS WARRANTIES STATED IN THIS SECTION 12, SELLER DOES
       NOT WARRANT THE MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE OF
       THE PRODUCTS OR THE PERFORMANCE OR NONINFRINGEMENT THEREOF, DOES NOT MAKE
       ANY WARRANTY, EXPRESS OR IMPLIED, WITH RESPECT TO PRODUCTS,
       SPECIFICATIONS, SUPPORT, SERVICE OR ANYTHING ELSE AND DOES NOT MAKE ANY
       WARRANTY TO NORTEL'S CUSTOMERS OR AGENTS. SELLER HAS NOT AUTHORIZED
       ANYONE TO MAKE ANY REPRESENTATION OR WARRANTY OTHER THAN AS PROVIDED
       ABOVE.

       EXCEPT IN RELATION TO DAMAGES, LIABILITIES, COSTS AND EXPENSES INCLUDED
       IN A JUDGMENT OR CLAIM COVERED BY THE INDEMNITY IN SECTION 19, UNDER NO
       CIRCUMSTANCES SHALL SELLER BE LIABLE FOR ANY INDIRECT, INCIDENTAL,
       SPECIAL, CONSEQUENTIAL, EXEMPLARY, PUNITIVE OR OTHER DAMAGES WHATSOEVER
       (INCLUDING DAMAGES FOR LOSS OF PROFITS, GOOD WILL, USE, DATA, OR OTHER
       INTANGIBLES) ARISING OUT OF OR RELATING TO ANY BREACH OF THE FOREGOING
       WARRANTIES EVEN IF SELLER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
       DAMAGES.

       THE FOREGOING LIMITATIONS SHALL BE APPLICABLE EVEN IF SUCH LIMITATIONS
       FAIL OF THEIR ESSENTIAL PURPOSE.

12.5   Any failure by Seller to execute its warranty obligations as contained in
       this Section 12 and Section 14 (Repair Services) shall constitute a
       material breach of Seller's obligations hereunder.

13.    REPAIR PROCEDURES
       -----------------

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13.1   This Section 13 shall be applicable to the providing of Repair Services
       described in Section 14 by Seller during and after the Product Warranty
       Period.

13.2   a)    Prior to returning any defective Products to the FCA Repair
             Location, Nortel will notify Seller orally of the defect, if known
             at that time, and will request authorization from Seller for the
             return of such Products. Upon such request, Seller shall provide
             Nortel with a Return Material Authorization ("RMA") number to be
             prominently displayed on the shipping container for the defective
             Products and advise Nortel of the FCA Repair Location to which the
             Products should be returned.

       b)    In all cases covered in Section 14 (Repair Services), [*]. Nortel
             shall prepare proper export documentation evidencing Nortel's
             ownership of the Products and shall comply with the requirements
             set forth in Exhibit J (NAFTA).

13.3   Nortel shall furnish the following information with Products returned to
       Seller for Repair Services:

       i)    Nortel's or the Nortel Company's name and complete address;
       ii)   quantities and model and serial numbers of Products being delivered
             for repair;
       iii)  the nature of the defect or failure, if known;
       iv)   Purchase Order number under which repairs are to be made, if
             Product is no longer under warranty;
       v)    name(s) and telephone number(s) of Nortel's employee(s) or other
             designated persons to contact in case of questions about the
             Products;
       vi)   ship-to address or Nortel's location to which repaired or
             replacement Products should be returned;
       vii)  whether or not returned Products are under warranty.

13.4   Seller shall date stamp each repaired and returned Product with the
       Repair Date and type of repair "pre fix" as per Bellcore GR-209
       specifications incorporated herein by reference and Specifications
       described in Exhibit B. Hardware repaired by Seller shall be stamped in
       accordance with requirements outlined in Bellcore TR-NWT-000078
       incorporated herein by reference. Without limiting the foregoing, the
       stamping shall include the Repair Date stenciled or otherwise identified
       in a permanent manner at a readily visible location on the Hardware,
       unless otherwise directed by Nortel.

13.5   Seller shall promptly provide a written notice to Nortel with the name(s)
       and telephone number(s) of the individual(s) to be contacted by
       designated Nortel personnel concerning any questions that may arise with
       respect to the Repair Services, and if required, specify any special
       packing of Products which might be necessary to provide adequate in-
       transit protection from transportation damage.

13.6   Once Products have been repaired or replaced by Seller, Seller shall
       reissue to Nortel an invoice for such repaired or replacement Products
       and the charges applicable to the providing of Repair Services, if any,
       as set forth in Exhibit D. Seller's invoice shall contain the following:

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       i)    Nortel's Purchase Order number for these Repair Services;
       ii)   a detailed description of the Repair Services provided by Seller
             and the need therefore;
       iii)  quantities and model numbers of Products repaired and associated
             repair charges;
       iv)   applicable sales or excise taxes;
       v)    total amount payable;
       vi)   address to which payment should be made.

13.7   The repaired or replacement Products shall be delivered by Seller to the
       destination specified by Nortel, [*]. Seller shall prepare proper export
       documentation as per Nortel's instructions, evidencing Nortel's ownership
       of the Products and shall comply with the requirements set forth in
       Exhibit J (NAFTA).

13.8   Seller shall promptly notify Nortel of returned Products which are found
       by Seller to be beyond repair. Products shall only be considered beyond
       repair after agreement of the Parties to that effect. All Products which
       are found to be beyond repair and not replaced shall be returned to
       Nortel at Nortel's discretion.

13.9   Nothing in this Agreement shall be construed as giving Seller an
       exclusive privilege to repair any Products covered under this Agreement;
       provided, however, that any repairs or modifications to the Hardware, or
       any attempt to do either by any third party not authorized by Seller,
       shall invalidate the warranties granted by Seller in Section 12
       (Warranty) above.

14.    REPAIR SERVICES
       ---------------

14.1   Repair Services shall be available to Nortel in accordance with the
       provisions contained in this Section 14 and in Section 13 (Repair
       Procedures).

14.2   This Section 14 shall be applicable to the providing of Repair Services
       by Seller during and after the Product Warranty Period.

14.3   To order Repair Services after expiry of the applicable Product Warranty
       Period, Nortel shall issue a Purchase Order and such Purchase Order shall
       contain the description of the requested Repair Services.

14.4   Repair Services for defects resulting from the breach of the warranty
       contained in Section 12 (Warranty) above shall be provided by Seller at
       no charge to Nortel during the Product Warranty Period. After expiry of
       the Product Warranty Period, Repair Services shall be at prices set forth
       in Exhibit D (Repair Services and Technical Assistance Rates) unless
       otherwise set forth in this Section 14 or unless covered by Section 5
       (Product and Process Changes).

14.5   Same-for-Same Repair Services
       -----------------------------

       The following procedures will apply:

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the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

       a)    Products returned to Seller for Repair Services shall be shipped by
             Nortel freight and insurance prepaid.

       b)    Seller shall track any defective Product by its unique serial
             number throughout the repair process.

       c)    Seller shall return, after having repaired and updated the Products
             to the minimum field baseline, the exact same Products having the
             same serial number. If the serial number has to change for any
             reason, Seller shall, on the `repair tag' originally provided by
             Nortel, document the following information: old serial number, new
             serial number and reason(s) for change.

       d)    Seller shall return any repaired Products with the `repair tag' or
             other mutually agreed to repair tag that was originally provided by
             Nortel with the defective Products. Seller shall provide all post-
             repair information as required on the `repair tag'.

       e)    Seller shall complete the Same-for-Same process within [*] of
             having received the defective Product.

14.6   Fast Cycle Failure Analysis
       ---------------------------

14.6.1 Seller shall perform a Fast Cycle Failure Analysis ("FCFA") at no cost to
       Nortel on Products which have caused any service interruption in the
       field or as may otherwise be reasonably requested by Nortel. Nortel will
       request a separate RMA number for each Product returned for an FCFA. An
       FCFA shall be performed by Seller in accordance with the following
       additional requirements:

       a)    FCFA shall include a detailed root cause analysis, using
             engineering tools such as Environment Stress Screening ("ESS") and
             any other tools which may be required to determine the cause of the
             failure.

       b)    Seller shall track any defective Product by its unique serial
             number throughout the repair process.

       c)    Seller shall return, after having repaired and updated the Products
             to the minimum field baseline, the exact same Products having the
             same serial number. If the serial number has to change for any
             reason, Seller shall, on the `repair tag' originally provided by
             Nortel, document the following information: old serial number, new
             serial number and reason(s) for change. This information will also
             be documented in the FCFA report. The Products shall not be
             "upgraded" to other than the actual unit release vintage until root
             cause analysis is completed and the Products successfully pass the
             complete test cycle. The Products shall not be repaired without
             completion of the FCFA activity.

       d)    Seller shall return the repaired Products with a written report
             documenting all findings as a result of the FCFA.

       e)    Seller shall complete the FCFA process within [*] of having
             received the defective Products at its Richardson, Texas plant.
             Nortel shall provide all available technical information to allow
             Seller to understand the circumstances and environmental conditions
             that led to the failure of the Products.

       f)    Seller shall inform Nortel of the return Product shipping
             information as soon as it is available. The shipping information
             will include, date shipped, carrier, waybill number and any other
             information that will help Nortel expedite the return of the
             Products.

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

       g)    In the event that the results of the FCFA indicate deficiencies
             with the Product Hardware or Software, then Seller will modify the
             Products to eliminate such deficiencies. Such modifications will be
             implemented in accordance with Section 5 (Product and Process
             Changes).

14.7   Products found defective within the first [*] from their initial
       utilization at customer site, (referred to as `Dead On Arrival' ("DOA")
       or Early Life Failure ("ELF") shall be returned to Seller along with the
       RMA documentation. Returned DOA/ELF Products shall be tested through full
       functional tests and ESS in order to provide a root cause analysis, then
       repaired, re-furbished, upgraded to the latest version or release,
       stamped with the Repair Date and returned to Nortel as new Products. Such
       testing and repairs will be done at no charge for those returned DOA/ELF
       Products which are within the Product Warranty Period; for those returned
       DOA/ELF Products which are not within the Product Warranty Period, Nortel
       shall pay the fee set forth in Exhibit D. Should the DOA/ELF occurrence
       represent more than [*] of the Products RR as defined in the
       Specifications, then Seller shall, in addition to performing root cause
       analysis, implement a corrective plan of action within [*] of this
       occurrence being reported. Seller will update Nortel in writing with the
       findings of the root cause analysis as well as with the corrective plan
       of action.

14.8   In case of a No Fault Found ("NFF") in respect of Products returned or if
       Nortel requests re-testing of Products reasonably known to Nortel as
       being in good condition, Seller shall invoice Nortel at the Prices
       specified in Exhibit D for their full functional tests and ESS and such
       Products shall be returned to Nortel after the tests are completed,
       freight collect using Nortel's designated carrier. Test turnaround time
       shall not exceed [*] from the date the Product is received at Seller
       facilities and a Purchase Order number has been received from Nortel.

14.9   Should the Product failures classified by Seller as NFF represent more
       than [*] of the Products RR as defined in the Specifications, then Seller
       shall, in addition to performing a root cause analysis, implement a
       corrective plan of action within [*] of this occurrence being reported.
       Seller will update Nortel in writing with the findings of the root cause
       analysis as well as with the corrective plan of action.


14.10  Emergency Replacement Products
       ------------------------------

       In emergency situations threatening continuity of service or Nortel end-
       user's in-service date, Seller shall in good faith, at Nortel's option,
       utilize reasonable commercial efforts to deliver to Nortel or its end-
       users, upon mutually agreeable terms, emergency replacement Products
       within [*] of Nortel's request, which may be conveyed to Seller by
       telephone or facsimile. All Products supplied under this Section shall be
       functionally equal or better than the vintage of the replaced units and
       must be backward compatible and meet the minimum field baseline.
       Emergency replacement Products shall be delivered via next day service
       and, for Products not within the Product Warranty Period, invoiced at
       rates then current for Products. Nortel agrees to pay such invoices
       within [*].

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

       Under this service, Seller will ship new units to the destination
       designated by Nortel, freight collect using Nortel's designated carrier
       within three (3) hours of Nortel's verbal request, such verbal request to
       be confirmed by Nortel in writing and transmitted by facsimile or other
       means of communications, prior to shipment of the units by Seller. In the
       case of shipment outside of the United States, Seller shall prepare
       proper export documentation as per Nortel's instructions, evidencing
       Nortel's ownership of the Product; customs clearance and duty fees (as
       applicable) shall be the responsibility of Nortel. This emergency service
       shall be available to Nortel through the following Seller's emergency
       telephone number 214-570- 3600.

15.    CONTINUING AVAILABILITY OF TECHNICAL ASSISTANCE, REPAIR SERVICES,
       -----------------------------------------------------------------
       MAINTENANCE, REPLACEMENT AND REPAIR PARTS
       -----------------------------------------

15.1   In no event shall the Products be discontinued until after the expiry of
       a period of [*], or such other period as may be agreed upon by the
       Parties, from Seller's written discontinuance notice to Nortel. Seller
       shall accept Releases and Purchase Orders submitted by Nortel within such
       period for any such affected Products.

15.2   Provided that this Agreement is not terminated due to the default or
       breach of Nortel, for a period of [*] after the discontinuance of a
       Product, Seller agrees to provide Repair Services on all Products ordered
       hereunder and to offer for sale to Nortel, functionally equivalent
       maintenance, replacement and repair parts as may be necessary for the
       continued maintenance of the Products, including discontinued Products.

15.3   Seller, upon supply discontinuance notices from its suppliers, of any
       sole source/critical components incorporated into the Products, shall
       notify Nortel immediately upon receipt of such notice. Seller shall
       endeavor to have its suppliers provide notices [*] in advance of
       discontinuance. Seller and Nortel shall determine the quantity of such
       components to be ordered as last time buy to cover for Nortel's spare
       parts requirements. Seller and Nortel will determine the quantity of such
       components to be ordered as last time buy to cover for spare maintenance,
       replacement and repair parts requirements as described in Section 14
       (Repair Services). Furthermore, should the unavailability of a component
       require Seller to develop a replacement product, Seller will jointly
       decide with Nortel on last time buys for such component to ensure
       continuity of supply until the replacement product is approved by Nortel
       and ready to be manufactured. The provisions contained in this Section
       15.3 shall be applicable for a period [*] after the expiry or termination
       of this Agreement.

15.4   Provided that this Agreement is not terminated due to the default or
       breach of Nortel, and provided that Nortel has paid all applicable fees,
       for a period of [*] after the discontinuance of a Product, Seller agrees
       to provide technical assistance in accordance with Section 16 (Technical
       Assistance and Marketing Support).

16.    TECHNICAL ASSISTANCE AND MARKETING SUPPORT
       ------------------------------------------

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

16.1   Technical assistance consists of those services described in this
       Section.

16.2   Product training shall be provided by Seller to Nortel as mutually agreed
       upon by the Parties.

16.3   In addition, Seller shall provide Nortel with Product training
       documentation and related information material as mutually agreed upon by
       the Parties.

16.4   All technical assistance rendered during the Product Warranty Period
       shall be provided to Nortel [*]. In all other cases, Seller's current
       rates applicable to technical assistance are those set forth in Exhibit
       D. Any technical assistance which Seller shall provide to Nortel or its
       customers shall be pursuant to a written request from Nortel's designated
       personnel, or such other individual that Nortel may from time to time
       designate. The availability or performance of technical assistance under
       this Section 16, shall not be construed as altering or affecting Seller's
       other obligations under this Agreement, including under Sections 6
       (Quality Control and Reliability Requirements, Supply Management and
       Nortel's Audit Rights), 12 (Warranty) and 5 (Product and Process
       Changes).

16.5   Seller shall provide technical assistance as set forth in this Section 16
       in order to facilitate the providing by Nortel of technical assistance to
       its customers. In order to facilitate Nortel's support of its customers,
       Seller shall provide to designated Nortel personnel only, [*] for a
       period of [*] following the expiration of this Agreement, telephone
       access to qualified Seller's technical personnel [*].

16.6   It shall be Nortel's responsibility to provide `first line' technical
       assistance to its customers.

16.7   Seller's failure to provide technical assistance as required under this
       Section 16 shall constitute a material breach of Seller's obligations
       hereunder.

16.8   Subject to the provisions set forth in Section 17, in order to assist
       Nortel in its Product related marketing activities, Seller shall provide
       Nortel with reasonable and mutually agreed upon marketing support.

16.9   Subject to the provisions set forth in Section 17, in order to assist
       Seller in its Product related marketing activities, Nortel shall provide
       Seller with reasonable and mutually agreed upon marketing support.

17.    DOCUMENTATION
       -------------

17.1   The Product Documentation shall be developed by Seller in accordance with
       the Specifications.

17.2   Seller shall provide, at no charge to Nortel, for each Product delivered
       one (1) set of the following Product Documentation in accordance with the
       Specifications: all Product descriptions, planning

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

       guides, operations manuals, installation manuals, and maintenance manuals
       normally provided by Seller to customers to facilitate their
       installation, use, and maintenance of the Products.

17.3   Seller shall supply to Nortel, at no additional charge, hard and
       electronic copies of Seller's Product Documentation (i.e., manuals,
       application notes and sales collateral) and any technical assistance
       reasonably required by Nortel and mutually agreed upon. Seller shall also
       continue to provide to Nortel, at no additional charge, during the Term
       of this Agreement any updates to Seller's Product Documentation, as soon
       as they are available.

17.4   Seller hereby grants to Nortel, at no cost, the limited and revocable
       right to use, copy, modify and translate the Product Documentation
       furnished hereunder solely for the purpose of providing such Product
       Documentation to Nortel's customers as a part and parcel of Nortel's sale
       of the Product to such customer; provided, however, that Nortel shall
       reproduce and include the copyright notice and any other notices or
       legends that appear in the Documentation in any copies or derivatives
       thereof.

17.5   Seller shall notify Nortel of any modifications to the Product
       Documentation in accordance with Section 5 (Product and Process Changes).

18.    CONFIDENTIAL INFORMATION
       ------------------------

18.1   It is expected that the Parties will disclose to each other certain
       business, marketing, technical, scientific or other information of any
       Party, including, without limitation, Specifications and Software which,
       at the time of disclosure, is designated as confidential (or like
       designation), is disclosed in circumstances of confidence, or would be
       understood by the Parties, exercising reasonable business judgment, to be
       confidential information ("Confidential Information") and each Party
       recognizes the value and importance of the protection of the other's
       Confidential Information. All Confidential Information owned or
       controlled by one Party and disclosed to the other Party shall remain
       solely the property of the disclosing Party, and its confidentiality
       shall be maintained and protected by the other Party with the same degree
       of care used to protect its own proprietary and confidential information
       of a similar nature, but no less than reasonable care, to prevent the
       unauthorized use, dissemination or publication of the Confidential
       Information. Except to the extent required or expressly permitted by this
       Agreement, both Parties agree not to duplicate or use in any manner the
       other's Confidential Information or to disclose it to any of their
       employees not having a need to know for the purposes of this Agreement or
       to any third party. The receiving Party's employees having a need to know
       the Confidential Information for the purpose of this Agreement may
       receive disclosure of the Confidential Information provided such
       employees are bound by confidentiality obligations no less stringent than
       those set forth in this Section 18. The confidentiality provisions
       contained herein shall survive the expiration or termination of this
       Agreement for a period of ten (10) years.

18.2   Confidential Information shall not include information which:

       a)    now is, or hereafter becomes, available to the public through no
             act or omission of the receiving Party; or
<PAGE>

       b)    is documented as being known by the receiving Party prior to its
             disclosure by the other Party; or

       c)    is independently developed by the receiving Party by persons who
             have not made reference to the Confidential Information and without
             recourse to any Confidential Information received under this
             Agreement and is so documented; or

       d)    is lawfully obtained by the receiving Party from a third party or
             parties without breach of confidentiality obligations or is
             disclosed hereafter to the receiving Party by a third party who did
             not acquire the information directly or indirectly from the
             disclosing Party; or

       e)    is disclosed in response to a valid order of a court or other
             governmental body or any political subdivision thereof, but only to
             the extent and for the purpose of such order and only if the
             receiving Party, to the extent possible, first notifies the
             disclosing Party, of such order and permits and reasonably assists
             it in seeking an appropriate protective order.

18.3   Subject to the restrictions and obligations of this Section 18,
       Confidential Information, nothing in this Agreement shall be interpreted
       or construed to limit either Party's right to perform or to continue to
       perform its own independent research, development, manufacturing or
       marketing of any type of Products or systems even if such research,
       development, manufacturing or marketing pertains to technology or
       products similar to the Products.

18.4   Subject to the exceptions set forth in this Section 18.4 (a) - (d) below,
       prior to the publication or use by a Party hereto of any advertising,
       sales promotions, press releases or other publicity matters relating to
       the Products or this Agreement in which the name or logo of the other
       Party is mentioned or language from which the connection of said name can
       be reasonably inferred or implied, each Party shall obtain the prior
       written consent of the other Party. Terms, conditions and general
       information of this Agreement shall be held in confidence by both Parties
       and only disclosed (a) as may be agreed to by both Parties, (b) as
       authorized in this Agreement, (c) to the receiving Party's insurers or
       financial or legal advisers under the terms of a confidentiality
       agreement with provisions substantially similar to those contained
       herein, or (d) as may be required to meet securities disclosure or export
       permit requirements provided, however, that the receiving Party shall
       attempt to preclude disclosure of the Confidential Information by means
       of an application for confidential treatment.

18.5   The Parties acknowledge and agree that a breach of this Section 18,
       Confidential Information, may result in irreparable and continuing harm
       to the disclosing Party for which there may be no adequate remedy at law.
       In the event of a breach or a threatened or intended breach of this
       Section 18 by the receiving Party, the receiving Party hereby consents to
       the granting of, and the disclosing Party shall be entitled to seek,
       preliminary injunctions unilaterally without notice, and final
       injunctions with notice, enjoining and restraining such breach, or
       threatened or intended breach, and to such other rights and remedies as
       are available at law or in equity to the disclosing Party except as
       expressly set forth herein.

18.6   Return Of Confidential Information: Upon request from the disclosing
       Party, the receiving Party shall (i) immediately return all Confidential
       Information and copies thereof; or (ii) immediately destroy such
       Confidential Information and all copies thereof, and certify their
       destruction to the
<PAGE>

       disclosing Party. The receiving Party's legal counsel may retain a single
       copy of Confidential Information for archival purposes only to provide a
       record of disclosure.

18.7   Proprietary Rights: The disclosing Party and its suppliers (as
       applicable) shall retain all right, title and interest in and to its
       Confidential Information. No license of any patent or copyright is
       granted to the receiving Party under this Agreement, except for the
       express rights granted in sections 19.5 and 29.

18.8   Liabilities: EXCEPT AS OTHERWISE PROVIDED IN THIS AGREEMENT, THE
       DISCLOSING PARTY HEREBY EXCLUDES ALL REPRESENTATIONS, WARRANTIES AND
       CONDITIONS, EXPRESS OR IMPLIED, INCLUDING ANY REPRESENTATIONS, WARRANTIES
       OR CONDITIONS OF ACCURACY, SUFFICIENCY, SUITABILITY OR NON-INFRINGEMENT.
       EXCEPT AS OTHERWISE PROVIDED IN THIS AGREEMENT, THE DISCLOSING PARTY
       SHALL HAVE NO LIABILITY WHATSOEVER FOR ANY DAMAGES, LOSSES OR EXPENSES
       INCURRED BY THE RECEIVING PARTY AS A RESULT OF ITS RECEIPT OF INFORMATION
       PURSUANT TO THIS AGREEMENT, WHETHER ARISING IN CONTRACT, TORT OR
       OTHERWISE. THE PARTIES ACKNOWLEDGE THAT THE LIMITATIONS DESCRIBED IN THIS
       SECTION AND THE ALLOCATION OF RISKS AND BENEFITS UNDER THIS AGREEMENT ARE
       A FUNDAMENTAL PART OF THIS AGREEMENT.

19.    INTELLECTUAL PROPERTY RIGHT INFRINGEMENT
       ----------------------------------------

19.1   Seller shall defend Nortel (including their directors, officers,
       employees and agents) against any and all proved and unproved claims
       brought by unrelated third parties against Nortel and shall hold Nortel
       and Subsidiaries harmless from and pay any corresponding damages,
       liabilities, costs and expenses (including reasonable attorney's fees)
       arising out of any proved or unproved claim that the use, sale and/or
       distribution of a Product delivered hereunder infringes any third-party
       patent, copyright, trademark, trade secret or other intellectual property
       right ("herein "Infringement Claim") provided that Nortel gives Seller
       prompt notice of, and authority to defend or settle, any such
       Infringement Claim and gives, at Seller's expense, reasonable information
       and assistance. Seller will notify Nortel if Seller is subject to any
       enquiry, allegation, claim or lawsuit in respect of patent, copyright,
       trade secret or other intellectual property right infringement regarding
       any Product delivered hereunder or any part thereof.

19.2   When notified of an action or motion that seeks to restrict the use, sale
       and/or distribution of any Product delivered hereunder, Seller may, (and
       in the case of a judgment, order or injunction that restricts the use,
       sale and/or distribution of any Product delivered hereunder shall), at
       its option and expense, (a) obtain the right for Nortel, Nortel
       Companies, distributors, end users and contractors, as applicable, to
       use, sell and/or distribute such Product delivered hereunder, (b)
       substitute other functionally equivalent product that does not infringe,
       or (c) modify such Product so that it no longer infringes.

19.3   In the event that Seller cannot perform under Section 19.2 (a) - (c)
       within [*] after the commencement of a judgment, order or injunction that
       restricts the use, sale and /or distribution of any Product purchased
       hereunder, this Agreement shall terminate in relation to the infringing

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

       Product and Nortel shall have the right to return such Products or
       portion thereof to Seller upon written notice to Seller, and, in the
       event of return, neither party shall have any further liabilities or
       obligations under this Agreement, except that Seller shall refund to
       Nortel the full Price paid for such returned Products within [*]
       following their return. Seller's indemnification obligations under this
       Section 19 shall survive with respect to those Products or portions
       thereof that have been previously distributed or sold by Nortel or Nortel
       Companies before commencement of the judgment, order or injunction.

19.4   The indemnity obligations under the foregoing provisions shall survive
       the termination or expiration of this Agreement.

19.5   The foregoing indemnification obligations shall not be applicable to the
       extent the Infringement Claim arises from:

       (a)   compliance of the Product with Nortel's designs; or

       (b)   modification by Nortel, Nortel Companies or their respective
             customers of the Product; or

       (c)   use of the Product by Nortel, Nortel Companies or their respective
             customers in combination with other products not provided by Seller
             provided the infringement arises from such combination and such
             combination was not contemplated by the Specifications or
             Documentation. If Seller becomes aware of any infringement or
             potential infringement which results from a combination identified
             in the Specifications, Documentation, or otherwise identified to
             Seller by a third party claiming an infringement or potential
             infringement, Seller will promptly notify Nortel of such
             infringement or potential infringement. If Seller fails to promptly
             notify Nortel of such infringement or potential infringement,
             Seller shall be liable to indemnify Nortel as set forth in this
             Section 19 of the Agreement.

       Nothing contained in this Agreement shall be deemed to grant, either
       directly or indirectly or by implication, any license under any patents
       or patent applications of Seller, except that Nortel shall have the
       normal non-exclusive, royalty-free license to use the Products as is
       implied, or otherwise arises by operation of law, due to Nortel's
       purchase of the Products and relates to the use, sale and/or distribution
       of the Products.

19.6   The foregoing is Nortel's sole and exclusive remedy and Seller's sole and
       exclusive liability relating to any Infringement Claim or any other claim
       of infringement of any intellectual or other proprietary or property
       right.

20.    HAZARDOUS MATERIALS
       -------------------

20.1   Seller shall identify and list in a notice forwarded to Nortel all of the
       hazardous or toxic materials which may be contained in the Products prior
       to shipping the Products. For the purposes of this Section 20.1, the
       hazardous and/or toxic materials shall be those identified or described
       by characteristics in the regulations promulgated under the applicable
       laws, rules and regulations of the United States, including, without
       limitation, the following: the Toxic Substances Control Act, Resource
       Conservation and Recovery Act of 1976, Hazardous Materials Transportation
       Act, Occupational Safety and Health Act of 1970, Comprehensive
       Environmental Response,

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

       Compensation and Liability Act of 1980, Consumer Product Safety Act,
       Radiation Control for Health and Safety Act of 1968, Clean Air Act, and
       Clean Water Act.

20.2   Seller shall periodically, but no less than annually, review the
       pertinent regulations and the materials contained in the Products and
       update the lists of hazardous and/or toxic materials accordingly. Upon
       request by Nortel, Seller shall also identify such other hazardous and/or
       toxic substances as Nortel may specify.

21.    INDEMNITY
       ---------

21.1   General
       -------

21.1.1 Each Party shall indemnify and save harmless as "Indemnitees" the other
       and its employees, officers and directors from and against any and all
       fines, penalties, losses, costs, damages, injuries, claims, expenses or
       liabilities as a result of injury to, or death of, any person, or damage
       to, or loss or destruction of, any property, arising out of, or resulting
       from, or in connection with, this Agreement or the performance of this
       Agreement and caused by the negligence or willful misconduct of the
       indemnifying Party or a contractor or an agent of the indemnifying Party
       or an employee of any one of them (hereinafter individually and
       collectively "Liabilities").

21.1.2 Upon request of an Indemnitee, the other Party shall, at no cost or
       expense to such Indemnitee, defend or settle any suit or other legal
       proceeding asserting a claim for Liabilities, and the other Party shall
       pay any reasonable costs and attorneys' fees that may be incurred by such
       Indemnitee in connection with any such claim, proceeding or suit.

21.1.3 The Indemnitee shall as soon as practicable notify the other Party of the
       assertion of any such claim of which the Indemnitee is aware and the
       other Party shall (a) keep the Indemnitee subject to any such claim fully
       informed as to the progress of such defense, and (b) afford such
       Indemnitee, each at its own expense, an opportunity to participate fully
       with the other Party in the defense or settlement of any such claim, but
       the other Party shall have sole control of any such settlement or
       defense.

22.    COMPLIANCE WITH LAWS
       --------------------

22.1   Seller represents and warrants that, to the best of its knowledge, it
       complies with and shall continue to comply with and has obtained and will
       continue to maintain in effect all licenses and permits required by, and
       Products shall be in conformance with, all applicable laws and
       governmental orders and regulations in effect in the United States and
       Canada at the time of the Delivery Date applicable thereto.

23.    CONSEQUENTIAL DAMAGES
       ---------------------

23.1   Except in relation to damages, liabilities, costs and expenses included
       in a judgment or claim covered by the indemnity in section 19, neither
       Party shall be liable pursuant to this Agreement for any incidental,
       consequential, special, exemplary, punitive or any other indirect damages
       or for
<PAGE>

       any damages for loss of profits or revenues even if the party has been
       advised of the possibility of such damages.

23.2   Except for a Party's indemnity obligations under Sections 19 or 21,
       Seller's breach of warranty under Section 13.1(c), or either Party's
       breach of Section 18, Confidential Information, in no event shall either
       party be liable for any damages in excess of the amounts paid by Nortel
       to Seller under this Agreement for Products and products in the twelve
       (12) months immediately preceding the institution of proceedings.

23.3   The limitations of this Section shall apply even in the event of the
       failure of their essential purpose.

24.    INSURANCE
       ---------

24.1   Seller shall procure and maintain in full force and effect during the
       period that this Agreement is in effect and for a period of [*], with an
       insurance company a Comprehensive General Liability insurance policy with
       third party liability coverage protecting Nortel and Nortel Companies
       against any loss, liability or expense due to bodily injury, death or
       property damage arising out of this Agreement or Products delivered
       hereunder, to the extent such loss, liability or expense is not due to
       the negligence of Nortel and any Nortel Company. Such policy shall have a
       combined single limit of a minimum of [*], shall provide coverage
       worldwide and shall not be restricted to occurrences in the country of
       insurer of Seller. Nortel and Nortel Companies shall be additional
       insureds under such insurance policy.

24.2   Nortel may upon [*] written notice request that Seller increase the
       foregoing minimum amount in order to comply with Nortel's obligations to
       any customer of any Products provided any such increase shall not exceed
       an amount equal to [*] of the applicable minimum amounts and shall be
       subject to the availability of such insurance. Following such request by
       Nortel, the Parties shall mutually agree on any increase and the amount
       of such increase and the allocation of payment obligations for any
       increased premium Seller incurs in obtaining such insurance.

24.3   Such policy shall be endorsed to be primary insurance and shall provide
       that it will not be cancelled or altered without at least [*] prior
       written notice to Nortel. Not later than [*] following the execution of
       this Agreement, Seller shall furnish Nortel with a certificate of such
       insurance and evidence that the premiums therefore have been paid.
       Maintenance of such insurance and the performance by Seller of its
       obligations under this Section 24 shall not relieve Seller of liability
       under the indemnity provisions set forth in this Agreement.

25.    FORCE MAJEURE
       -------------

25.1   Except for a Party's payment obligations under this Agreement, if the
       performance of any obligation under this Agreement or a Release or
       Purchase Order is interfered with by reason of any circumstances beyond
       the reasonable control of the Party affected, including, without
       limitation,

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

       fire, explosion, power failure, acts of God, war, revolution, civil
       commotion, delays of the other Party in the performance of any of its
       obligations hereunder, acts of the public enemy, or any law, order,
       regulation, ordinance or requirement of any government or legal body, and
       labor difficulties, including without limitation, strikes, slowdowns,
       picketing or boycotts; then the Party affected shall be excused from such
       performance for a period equal to the delay resulting from any such
       causes and such additional period as may be reasonably necessary to allow
       the Party to resume its obligations, (and the other Party shall likewise
       be excused from performance of its obligations to the extent such Party's
       obligations relate to the performance which was interfered with). The
       Party so affected shall make reasonable efforts to remove such causes of
       nonperformance; provided, however, in the event any such cause of
       nonperformance extends for more than [*], Nortel shall have the right,
       without obligation or liability, to cancel any Release or Purchase Order
       affected by such cause.

25.2   Either Party shall notify the other Party in writing within [*] after
       becoming aware of the occurrence of any force majeure event which may
       cause any delay or failure on the part of such Party to perform its
       obligations hereunder.

26.    TERM
       ----

26.1   This Agreement shall become effective on the Effective Date and shall
       remain in effect for a period of [*] ("Initial Term") [*] unless one
       Party gives to the other Party a notice to the effect that this Agreement
       will not be renewed, individually and collectively such period(s) being
       referred to herein as "Term", unless and until terminated in accordance
       with this Agreement.

27.    TERMINATION AND CONTINUING RIGHTS
       ---------------------------------

27.1   The Agreement may be terminated upon notice by one Party, at its sole
       discretion, in the event the other Party is affected by any one of the
       following events:

       a)    the institution by one Party of insolvency, receivership or
             bankruptcy proceedings or any other material proceedings for the
             settlement of its debts, including, without limitation, a
             reorganization, a compromise, an arrangement or assignment for the
             benefit of its creditors; the institution of such proceedings
             against a Party which such Party has failed to resolve in its favor
             within [*] in the case of involuntary proceedings or [*] in the
             case of voluntary proceedings, after appropriate services of
             process; a Party making a general assignment for the benefit of
             creditors; or a Party's dissolution or ceasing to do business in
             the normal course; or

       b)    has a substantial part of its assets seized; or

       c)    assigns the Agreement or any part thereof in violation of
             Section 31.4 (Assignment);

       the affected Party is obliged to immediately give notice to the other of
       the occurrence of any such event.

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

27.2   The Agreement and/or any Purchase Order or Release may be terminated, in
       whole or in part, by Nortel, upon written notice to Seller, in the event
       another party acquires a controlling interest in Seller (controlling
       requiring greater than 50% of voting stock) or a majority equity
       participation in Seller, without a written guarantee from such party to
       Nortel that such party will continue to abide by the terms of this
       Agreement within thirty(30) Business Days of such party assuming control
       or a majority equity interest.

27.3   The Agreement and/or any Purchase Order or Release may be terminated, in
       whole or in part by either Party, upon a [*] written notice, in the event
       the other Party fails to execute any one of its material obligations
       hereunder and fails to remedy the default within said period of [*].

27.4   Above termination rights shall be in addition to other termination rights
       contained herein, including under Sections 8 (Delivery) and 9 (Prices and
       Payment), and shall be without prejudice to the rights or claims one
       Party may have against the other with respect to the performance,
       nonperformance, or breach of such Party's obligations hereunder, and
       shall not operate so as to extinguish any rights or obligations which
       arose prior to the date of termination, and each Party shall have the
       right to pursue each and every available remedy at law and in equity,
       including, without limitation, withholding payments of any undisputed
       amount owed by Nortel to Seller pending resolution of any claims made by
       Nortel in good faith against Seller.

27.5   In the event this Agreement is terminated by Seller for default by Nortel
       or for any other reason hereunder, Nortel and its customers shall
       thereafter retain the right to purchase Repair Services and Product
       support and maintenance under terms and conditions mutually agreed upon
       by the Parties.

27.6   This Agreement may be terminated upon agreement of the Parties to that
       effect.

27.7   Notwithstanding any termination or expiry of this Agreement, the
       provisions of Sections 1 (Definitions), 5 (Product and Process Changes),
       9 (Prices and Payments), 12 (Warranty), 15 (Continuing Availability of
       Technical Assistance, Repair Services, Maintenance, Replacement and
       Repair Parts), 18 (Confidential Information), 19 (Intellectual Property
       Right Infringement), 21 (Indemnity), 23 (Consequential Damages), 27
       (Termination and Continuing Rights), 28 (Notices), 30 (Governing Law),
       and 31 (General) shall survive the termination or expiry of this
       Agreement.

28.    NOTICES
       -------

28.1   Any and all notices or other information to be given by one of the
       Parties to the other hereunder shall be sent by registered or certified
       mail, postage prepaid, return receipt requested or by overnight delivery
       service which provides written receipt of delivery, or by confirmed fax
       or hand delivery to the other Party at the addresses set forth in
       Exhibit K.

28.2   Notices given pursuant to Section 28.1 shall be deemed to have been
       received five (5) Business Days after mailing if given by mail, and one
       business day after sending if given by telecopy or overnight delivery
       service and upon delivery if given by hand.

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

28.3   Either Party may change its address at any time by giving fifteen (15)
       Business Days prior written notice to the other Party as provided above.

29.    CONTINGENT LICENSE
       ------------------

29.1   To ensure uninterrupted availability of the Products and ongoing
       maintenance and support for such Products, including Repair Services, in
       the event of (i) Seller's insolvency, receivership or bankruptcy
       proceedings or any other material proceedings for the settlement of its
       debts, including, without limitation, a reorganization, a compromise, an
       arrangement or assignment for the benefit of its creditors; the
       institution of such proceedings against Seller which Seller has failed to
       resolve in its favor within [*] after appropriate services of process;
       (ii) Seller making a general assignment for the benefit of creditors; or
       (iii) Seller's dissolution or ceasing to do business in the normal
       course; then Seller shall, at no additional charge, furnish to Nortel a
       license to use and have manufactured the Products for the duration of the
       Term. Should such use or manufacture of the Products, due to the
       occurrence of either (i), (ii) or (iii) above, involve the practice of
       any invention covered by a patent, Seller shall not assert such patent
       against Nortel.

30.    GOVERNING LAW
       -------------

30.1   The validity, construction, interpretation and performance of this
       Agreement and the rights and obligations of the Parties and any purchase
       made hereunder shall be governed by the courts and laws of the [*],
       except for its rules with respect to the conflict of laws. The
       application of the U.N. Convention on Contracts for the International
       Sale of Goods is specifically excluded from this Agreement.

31.    GENERAL
       -------

31.1   Severability
       ------------

       If any of the provisions of this Agreement shall be adjudged invalid or
       unenforceable, such invalidity or unenforceability shall not invalidate
       or render this Agreement unenforceable, but rather this Agreement shall
       be construed as if not containing the particular invalid or unenforceable
       provision or provisions, and the rights and obligations of the Parties
       shall be construed and enforced accordingly, provided that, in the event
       either Nortel or Seller would not have entered into this Agreement
       without such provision, that Party shall have the right to terminate this
       Agreement upon written notice to the other Party.

31.2   North America Free Trade Agreement - Procedures
       -----------------------------------------------

       Seller shall assist Nortel in performing all administrative actions
       required to qualify Products for preferential treatment under the rules
       of any applicable trade pursuant to the procedures set out in Exhibit J.

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

31.3   Debarment Certificate
       ---------------------

       Seller shall promptly, upon written request of Nortel, provide a properly
       executed certificate in the form attached as Exhibit I (as such form may
       be modified from time to time by the United States Rural Utilities
       Service) and in accordance with the requirements specified therein with
       respect to any Products furnished by Seller and which Nortel provides to
       a customer which requires Nortel to provide a similar certificate. Seller
       will comply with clause 52.244-6 of the Federal Acquisition Regulations
       ("FAR"), including all FAR provisions referenced therein, in effect as of
       the Effective Date of this Agreement. Seller disclaims, and disclaims
       compliance with, any other FARs, including but not limited to those
       concerning cost and pricing data and/or cost accounting standards.

31.4   Assignment
       ----------

       Neither Party shall assign or otherwise transfer all or any part of this
       Agreement or any rights or payments to be made hereunder (by way of a
       written assignment and/or change of control), or any interest herein,
       without the prior written consent of the other Party, except that Nortel
       may assign or subcontract any of its rights or obligations hereunder to
       any Nortel Subsidiary and Seller may assign to a successor in interest
       which acquires all or substantially all of the assets or control of
       Seller provided that such successor [*], controlled by or under common
       control with [*]. For purposes of this provision, "control" of an entity
       means the power to direct or cause the direction of the management and
       policies of such entity through the ownership of more than fifty percent
       (50%) of the voting securities of such entity.

31.5   Waiver
       ------

       Except as specifically provided for in a waiver signed by duly authorized
       representatives of Nortel and Seller, failure by either Party at any time
       to require performance by the other Party or to claim a breach of or to
       enforce any provision of this Agreement shall not be construed as
       affecting any subsequent breach or the right to require performance with
       respect thereto or to claim a breach with respect thereto and shall not
       constitute a waiver of such provisions or the right of such Party to
       enforce each and every provision.

31.6   Independent Contractors
       -----------------------

       Nortel and Seller are independent contractors in all relationships and
       actions under and contemplated by this Agreement. This Agreement shall
       not be construed to create or to authorize the creation of any
       employment, partnership or agency relation, or to authorize Nortel or
       Seller to enter into or make any commitment, agreement, representation or
       warranty binding on the other, or to allow one Party to accept service of
       any legal process addressed to, or intended for, the other Party. Nothing
       contained in this Agreement shall limit, in any manner, either Party's
       right to enter into other agreements with other parties.

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

31.7   Section Headings
       ----------------

       Section headings are inserted herein for convenience only and shall not
       affect the meaning or interpretation of this Agreement or any provision
       hereof.

31.8   Entire Agreement
       ----------------

       This Agreement, including Exhibits A through K attached hereto, comprises
       all the terms, conditions and agreements of the Parties hereto with
       respect to the subject matter herein, and save as expressly provided
       herein, may not be altered or amended except in writing signed by
       authorized representatives of each Party hereto. This Agreement may not
       be varied except through a document agreed to and signed by both Parties.

31.9   Each party agrees that, during the term of this Agreement, a party will
       not solicit the employees of the other party. This nonsolicitation
       restriction does not prohibit either party from using general recruiting
       strategies that are not directed specifically towards the other party's
       employees, including, but not limited to, the placement of advertisements
       or web-site postings regarding employment opportunities or from hiring
       any such employee if such employee seeks employment in response to such
       general solicitation and without individual, personal solicitation by the
       hiring party as the first contact with such employee.



IN WITNESS WHEREOF, the Parties hereto have executed this Agreement on the day
and year last written below.

CHORUM TECHNOLOGIES                     NORTEL NETWORKS LIMITED
INCORPORATED
By:  /s/ Kent Coker                     By:
    ---------------------------            ---------------------------
        (Signature)                           (Signature)

Name:    Kent Coker                     Name:
     --------------------------              -------------------------
        (Print)                               (Print)

Title:   CFO                            Title:
      -------------------------               ------------------------

Date:    10/13/00                       Date:
     --------------------------              -------------------------
<PAGE>

                                   EXHIBIT A
                                   ---------

             PRODUCT LISTS, PART I AND PART II, PRICES, DISCOUNTS,
             -----------------------------------------------------
                 AVAILABILITY DATES AND FCA DELIVERY LOCATIONS
                 ---------------------------------------------


Part I:  Product List:  Accepted Products, Prices and Discounts
                        ---------------------------------------

[*]


** represents the percentage of Nortel's capacity plan of [*] (represented by *)
that Nortel will allocate to Seller.

For avoidance of doubt, in the event that CPC Codes change, such successor
products will be subject to this guaranteed allocation.

Part II:  Product List:  Non-accepted products, Prices, Discounts and
                         --------------------------------------------
Availability Dates
------------------

To be determined


Part III:  FCA Delivery Locations

[*]

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

                                   EXHIBIT B
                                   ---------

                     SPECIFICATIONS AND ACCEPTANCE PROGRAM
                     -------------------------------------


Part I:     Specifications

1.   Document Identification:

[*]

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

2.   Certification

     Seller shall use reasonable due diligence to pursue the certifications
     listed below (as applicable) as soon as new or modified designs have passed
     Seller's production release milestone without prejudice to Nortel's
     Acceptance Program outlined in Exhibit B, Part II. Seller and Nortel shall
     arrange for joint submission to the regulatory bodies and Nortel shall
     repay Seller the additional costs incurred through the joint submissions.
     All Changes to existing designs that could invalidate any one of the
     certifications shall be discussed between Seller and Nortel as part of the
     Change Notification procedure even if they do not require a production
     release.
<PAGE>

       The list of required certifications will be mutually agreed to in good
       faith and may include those below:

       CEMark
       UK Type Approval
       UL / CSA / EN safety
       FCC parts 15 and 101

       Should other certifications be required, they shall be discussed between
       Seller and Nortel. Seller shall use its reasonable commercial efforts to
       support Nortel's regulatory activities.

       Support groups:     Seller's Support Engineering group
       --------------
                           Nortel's Design Engineering group.

Part II:     Product Acceptance Program

1.     In order to verify that the products or modified Products meet the
       applicable Specifications, Nortel will undertake an Acceptance Program
       covering verification and product integrity testing.

2.     Seller, upon mutually agreeable terms, shall provide the products
       necessary to perform the Acceptance Program to Nortel and shall provide
       support to the applicable Nortel group during the testing. Such support
       includes diligence in replacing failed products, availability of
       technically knowledgeable individuals to discuss testing results and
       teaming of at least one individual from Seller with the Nortel testing
       group for all tests to occur on Seller's premises.

3.     At a minimum, each new design shall be tested by Nortel's Design
       Engineering team.

4.     Primeships:

       Nortel Networks Design Engineering group is prime for the verification
       testing;
       Seller's Support Engineering group is prime for supporting Nortel's
       Acceptance Program.

PART III:    Product Marking

       In absence of a Product Specification that defines Product Marking, the
       following shall apply:

1.     Serial number:  bar-coded serial number, as per relevant Specifications

2.     Manufacturing date stamp: Seller stamps date as agreed upon by the
       Parties.

3.     Seller's model number as agreed upon by the Parties.

4.     Nortel's CPC will be placed on the module.
<PAGE>

5.     Repair Date Stamp:  Bellcore TR-NWT-000078 (issue 3, December 1991),
       section 12.2. The location code for Seller ("LL") and how Seller rubber
       stamps shall be mutually agreed upon by the Parties.

6.     Product marking and packaging requirements pursuant to this Agreement:

       a)    Nortel's Corporate Standard CS152.50 on product integrity;

       b)    Bellcore GR-CORE-1421 and TR-NWT-000063;

       c)    Nortel's Corporate Standard 157.0 and Bellcore TR-NWT-870 on ESD
             protection;

       d)    Nortel's Quality System Procedure EXCESDO1.STL.

       Seller shall package the Products for shipment in accordance with
       Bellcore's GR-CORE-1421, TR-NWT-000063 and TR-NWT-870 standard packing
       practices. Any modifications specified by Nortel which are related to the
       size and external markings (including branding) of the boxes shall be
       agreed upon by Seller. Seller shall be responsible for any damage to
       Products including damage caused by packing noncompliant with Bellcore
       requirements.

7.     Cables:  As per relevant Specifications.
<PAGE>

                                   EXHIBIT C
                                   ---------

                              DEMAND-PULL PROGRAM
                              -------------------


1.     SCOPE

1.1    This Exhibit C sets forth the terms and conditions applicable to the
       ordering of Products pursuant to the Demand-Pull Program.

2.     NORTEL'S RESPONSIBILITIES

2.1    For Products that are ordered under the Demand-Pull Program Nortel shall,
       on the first business day of each week during the Term, provide Seller
       with a twelve (12) month rolling forecast ("Forecast") of its Product
       requirements, if any. Concurrently with its presentation of the first
       Forecast to Seller, Nortel shall issue an annual firm Blanket Purchase
       Order for the quantity of Products shown on such Forecast. Releases for
       Products covered by a Blanket Purchase Order issued under this Section
       will be issued in accordance with Nortel's designated purchasing
       department representative's weekly demands. If a required Forecast update
       is not timely submitted for a Product, the immediately preceding week
       Forecast shall become the new Forecast and/or Release; if there is no
       Forecast from the immediately preceding week, the Forecast for the most
       recent preceding week shall become the Forecast and/or Release. Nortel's
       Forecasts and Blanket Purchase Orders shall reflect its good-faith
       expectations of customer demand and Nortel shall act in a commercially
       reasonable manner to schedule orders to avoid creating production
       capacity problems for Seller.

2.2    Attachment A sets forth the applicable Product stocking requirements
       stated on a Target Finished Goods ("Target FG") and Target Work-In
       Process (modules, dies components and parts) ("Target WIP") basis,
       (collectively referred to as "Target Products Total Stock"). The Target
       Products Total Stock will be jointly established by the Parties in
       writing based on the run rate and agreed upon number of weeks, as
       referred to in Section 3.2 hereof, taking into consideration the Seller's
       Products manufacturing lead time as well as the unique component
       purchasing lead time, all as stated in Attachments A and B hereof. The
       Target Products Total Stock shall be jointly monitored and may be revised
       by agreement of the Parties in writing as fluctuations in the run rate so
       require and Attachment A updated accordingly.

2.3    [*].

2.4    [*]

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

3.     THE SELLER'S RESPONSIBILITIES

3.1    Seller shall manufacture the Target Products Total Stock in accordance
       with the run rate as set forth in Attachment A which may be revised as
       provided hereunder but shall only deliver Products per latest written
       instruction from Nortel.

3.2    Seller shall maintain Target FG and Target WIP quantities representing a
       maximum of [*], respectively, of the run rate set forth in Attachment A
       which may be revised as provided hereunder.

3.3    Seller's manufacturing operations and processes shall be established and
       maintained throughout the Term so that Seller is able to comply with
       Section 8.5.4 of the Agreement.

3.4    Products ordered pursuant to the Demand-Pull Program shall be delivered
       FCA [*].

3.5    Seller shall provide to Nortel's designated Purchasing Department
       representative a weekly report of Seller's Actual Products Total Stock
       status.

4.     CANCELLATION OF THE DEMAND-PULL PROGRAM

4.1    Nortel may terminate the Demand-Pull Program in whole or in part by means
       of a written notice to that effect, forwarded to Seller at least [*] in
       advance. Should the Demand-Pull Program be terminated, and if Nortel
       cancels a Blanket Purchase Order, Nortel may issue other Purchase Orders
       for Products that were contained in the cancelled Blanket Purchase Order
       ("Substitute PO"). In the event Nortel does not issue a Substitute PO(s),
       the cancellation charges set forth in Section 8.7 shall be applicable to
       such cancelled Blanket Purchase Order.

4.2    Nortel's obligation to purchase under this Agreement is set forth in
       Section 8.

4.3    Nortel's obligation to purchase under this Agreement shall be reduced by
       the amount of Products that can be purchased by Purchase Orders or that
       may be purchased by other customers of Seller. In addition, Seller shall
       use all reasonable endeavors to minimize any such costs by, inter alia,
       returning components to suppliers or reducing cancellation costs to
       suppliers, and such savings will be passed on to Nortel.

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

                                 ATTACHMENT A

                                                               WEEK:    ________

<TABLE>
<CAPTION>

---------------------------------------------------------------------------------------------------------------------------
                                          RUN           TARGET          TARGET        ACTUAL        ACTUAL         LEAD
CPC NO.             DESCRIPTION          RATE           FG STK           WIP          FG STK         WIP           TIME
---------------------------------------------------------------------------------------------------------------------------
<S>                 <C>                  <C>            <C>             <C>           <C>           <C>            <C>

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------
</TABLE>


                 NORTEL APPROVAL:                ______________________________
                 DATE:_____________
                 SELLER APPROVAL:                ______________________________
                 DATE:___________________
<PAGE>

                                 ATTACHMENT B


STRATEGIC  SUPPLIER MANAGEMENT

DEMAND-PULL PROGRAM - Unique Components

SUPPLIER:
          ---------------------------------------------------------------------
CONTACT:
          ---------------------------------------------------------------------
TEL. NO.
          ---------------------------------------------------------------------

<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------------------
 Supplier                  Description                 Supplier Safety          WIP @ supplier (weeks)
 Product                                                Stock (weeks)
------------------------------------------------------------------------------------------------------------
<S>                        <C>                         <C>                      <C>
------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------
</TABLE>
<PAGE>

                                   EXHIBIT D
                                   ---------

     REPAIR SERVICES RATES, FCA REPAIR LOCATIONS AND TECHNICAL ASSISTANCE RATES
     --------------------------------------------------------------------------



I.     TECHNICAL ASSISTANCE RATES
       --------------------------

             [*].


II.    FCA REPAIR LOCATIONS
       --------------------

             [*]


III.   REPAIR SERVICES RATES
       ---------------------


             [*].

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

                                   EXHIBIT E
                                   ---------


The method of transmission of information, Purchase Orders, Blanket Purchase
----------------------------------------------------------------------------
Orders, Releases, acknowledgments and invoices will be mutually agreed upon by
------------------------------------------------------------------------------
the Parties.  The provisions set forth below in Part I and II are for example
-----------------------------------------------------------------------------
purposes only and will not apply unless mutually agreed upon by the Parties.
-----------------------------------------------------------------------------


                  PROCEDURES FOR ORDERS UTILIZING EDI AND TDI
                  -------------------------------------------
                              (REV NAESGA_970321)

                                    PART I
               Electronic Data Interchange ("EDI") Transmission

This Part I of Exhibit E contemplates EDI transmissions of information and
Purchase Orders, Blanket Purchase Orders, Transaction Set 850 Releases or
EDIFACT 2.0 P.O. Releases (collectively, in this Exhibit E, "Orders"),
acknowledgments and invoices.  The EDI transactions shall be governed by the
Agreement, as modified by this Part I of Exhibit E.  This Part I of Exhibit E
shall not apply to Orders delivered solely in hard copy document form.

EDI transactions shall be made through a third-party computer network with which
the Nortel Companies and Seller have a services agreement ("Network").  EDI
transactions shall be made in accordance with the version of either 1) the
American National Standards Institute ("ANSI") Business Data Interchange
Standards ANSI X12, or 2) Electronic Data Interchange for Administration,
Commerce and Transportation Issue No. 2.0 ("EDIFACT"), which each Nortel Company
then utilizes, inclusive of transaction sets or comparable EDIFACT electronic
messages, data dictionary, data elements and transmission control.  Each party
shall be responsible for its respective costs incurred in sending and receiving
EDI transmissions.

Seller shall access at least once on each business day the Network to determine
whether it has received any Orders (ANSI X12, Transaction Set 850 or EDIFACT 2.0
ORDERS).  A functional Acknowledgment of Receipt of Transmission (ANSI X12,
Transaction Set 997) or an EDIFACT functional Acknowledgment Receipt of P.O.
Message shall be transmitted immediately upon receipt of an EDI Order.  A full
Transaction Acknowledgment (ANSI X12, Transaction Set 855 or EDIFACT 2.0 ORDSP)
shall be transmitted by Seller within two (2) Business Days after transmittal of
the functional Acknowledgment of Receipt of Transmission.  Each Order shall
contain and each full Transaction Acknowledgment shall confirm the price,
quantity, Product description by part number, FCA Delivery Location, location to
which the invoice shall be rendered for payment, method of shipment, Delivery
Date.

To reschedule, cancel or otherwise change an Order, a Nortel Company shall
transmit a Purchase Order Change (ANSI X12, Transaction Set 860 or EDIFACT 2.0
ORDCHG) and Seller shall transmit a Purchase Order Change Acknowledgment (ANSI
X12, Transaction Set 865 or EDIFACT 2.0 ORDSP) to the appropriate Nortel Company
within two (2) Business Days after receipt by Seller of the Purchase Order
Change.
<PAGE>

Any forecast information shall be sent using ANSI X12, Transaction Set 830 with
a quantity status code of "D" shown in the applicable time period field or
EDIFACT 2.0 DELFOR with a delivery plan status indicator of 4.  A Transaction
Set 830 Release (ANSI X12, Transaction Set 830 with a quantity status code of
"C" shown in the applicable time period field on such Transaction Set) or
EDIFACT 2.0 DELFOR with a delivery plan status indicator of 1 shall be
transmitted by a Nortel Company to confirm a Delivery Date for specific
quantities of Products covered by a Blanket Purchase Order, where that Nortel
Company requires Seller to send an Advanced Shipment Notice (ANSI X12,
Transaction Set 856 or EDIFACT 2.0 DESADV) prior to shipment.  Upon receipt of
such Transaction Set 830 Release or EDIFACT 2.0 DELFOR, Seller shall transmit to
the Nortel Company such Advanced Shipment Notice not less than the number of
days agreed upon between the FCA Delivery Location and Seller prior to shipment
of the quantity of Products covered by such Transaction Set 830 Release or
EDIFACT 2.0 DELFOR.

Each Nortel Company ordering under this Agreement shall access the Network at
least once on each Business Day to determine whether it has received any
"Invoices" (ANSI X12, Transaction Set 810 or EDIFACT 2.0 INVOIC).  A functional
Acknowledgment of Receipt of Transmission (ANSI X12, Transaction Set 997 or
comparable EDIFACT 2.0 electronic message) shall be transmitted immediately upon
receipt of an Invoice.

A Nortel Company shall not have any liability to Seller for Orders or Invoices
erroneously transmitted to or received by Seller due to the malfunction of or a
defect in the Network or other causes beyond a Nortel Company's reasonable
control.  If Seller receives a distorted EDI transmission, Seller shall
immediately contact the Network to reject the distorted transmission and request
that such transmission be resent.  If Seller receives an Order by EDI
transmission stating a quantity and/or price significantly higher or lower than
the typical quantity and/or Price shown on Orders issued by that Nortel Company
ordering location, Seller shall immediately contact such ordering location to
confirm the accuracy of the electronically transmitted Order.

Each Party shall adopt as its signature an electronic identification consisting
of symbol(s) or code(s) which shall be affixed to or contained in each document
transmitted by such Party ("Signatures").  Each Party agrees that its Signature
shall be sufficient to verify that such Party originated and authorized such
document.  Each Party shall use reasonable efforts to not disclose the Signature
of the other Party to any unauthorized third party.

Any document properly transmitted pursuant to this Part I of Exhibit E shall be
deemed to be a "writing" or "in writing", and any such document when containing,
or to which there is affixed, a Signature ("Signed Documents") shall be deemed
for all purposes (a) to have been duly authorized and executed and (b) to
constitute an "original" when printed from electronic files or records
established and maintained in the normal course of business.  The Parties agree
not to contest the validity or enforceability of Signed Documents under the
provisions of any applicable law relating to whether certain agreements are to
be in writing or signed by the Party to be bound thereby.  Signed Documents, if
introduced as evidence on paper in any judicial, arbitration, mediation or
administrative proceedings, shall be admissible as between the Parties to the
same extent and under the same conditions as other business records originated
and maintained in documentary form.
<PAGE>

                                    Part II
                TECHNICAL Data Interchange ("TDI") Transmission

This Part II of Exhibit E contemplates the electronic transmission of various
types of data files, including but not limited to engineering and material
specifications, drawings, computer-aided designs ("CADs"), models, plot and flat
files ("Technical Data Interchange" or "TDI").  The TDI transmissions between
each Nortel Company and Seller shall be governed by the Agreement and this Part
II of Exhibit E.

TDI transmissions shall be made through a third-party computer network with
which each of the Nortel Companies and Seller have a services agreement
("Network").  Each Party shall be responsible for its respective costs incurred
in sending and receiving TDI transmissions.

Seller shall access the Network at least once on each Business Day to determine
whether it has received any TDI transmissions.

Seller acknowledges and agrees that a Nortel Company shall not have any
liability for TDI transmissions erroneously transmitted to or received by Seller
due to a malfunction of or a defect in the Network or other causes beyond a
Nortel Company's reasonable control.  If Seller receives a distorted TDI
transmission, Seller shall immediately contact the Network to reject the
distorted transmission and request that such transmission be resent.

Seller shall comply with such security precautions and rules as may be initiated
by the Network to protect TDI transmissions from unauthorized access.  Seller
shall treat each TDI transmission as confidential information under the
applicable provisions of the Agreement.

Each Party shall adopt as its signature an electronic identification consisting
of symbol(s) or code(s) which shall be affixed to or contained in each document
transmitted by such Party ("Signature").  Each Party agrees that its Signature
shall be sufficient to verify that such Party originated such document.  Each
Party shall use reasonable efforts to not disclose the Signature of the other
Party to any unauthorized third party.
<PAGE>

                                   EXHIBIT F
                                   ---------

                                MONTHLY REPORTS
                                ---------------


Seller agrees to use reasonable commercial efforts to provide the reports set
-----------------------------------------------------------------------------
forth in this Exhibit as requested in writing by Nortel.
--------------------------------------------------------


1.     Seller will provide monthly reports in the following areas:

       a)    Repair and Return;

       b)    Baseline Report;

       c)    General Business.

2.     Seller shall provide a Unit Failure Analysis report on all field returned
       Products and a Component Failure Analysis report on a monthly basis to
       Nortel's Repair Manager, to Nortel's Quality Manager and to Nortel's
       Product Brand Manager. This report which will be issued no later than
       three (3) Business Days after the start of every month shall contain the
       following information:

       a)    The number of Products delivered to Nortel (on a per PEC level)
             in previous month.

       b)    The number of Products returned to Seller (on a per PEC level) in
             previous month.

       c)    The number of Products delivered to Nortel (on a per PEC level)
             year to date.

       d)    The number of Products returned to Seller (on a per PEC level)
             year to date.

       e)    The number of Products delivered to Nortel (on a per PEC level)
             to date.

       f)    The number of Products returned to Seller (on a per PEC level) to
             date.

       g)    Pareto of replacement devices of current month per PEC code.

       h)    Pareto of replacement devices cumulative per PEC code.

       i)    Post Repair Information on a per unit basis returned to Seller for
             repair under the "like-for-like" program for the previous month to
             include the following information:
             - Symptoms of replacement devices per unit;
             - Cumulative In-service time (in months) per PEC code;
             - Annualized replacement rate per PEC code.

       j)    Trend chart in time of replacement rate value (RpR)

       k)    Actual MTBF measurement. Actual annualized MTBF will be calculated
             from the cumulative replacement rate recorded monthly. Based on
             results, additional requirements can be determined upon agreement
             of both Parties.

       l)    On Time service level for 1) Repair and Return 2) Retrofit 3)
             FCFA 4) RMA.

       For all occurrences of Product failure in the field, analysis results,
       corrective actions and implementation plan have to be included in the
       monthly report.

3.     From the date the Products will have successfully passed the Acceptance
       Program in accordance with Section 4 of the Agreement, Seller shall
       provide to Nortel's Repair Manager, to Nortel's Quality Manager and to
       Nortel's Product Brand Manager a monthly "Minimum Field Baseline" report
       indicating the minimum applicable release level (number) for the in-
       service operation of the Products and a "New Product Shipped Baseline".
       The reports shall provide the details of specific Product releases for
       each applicable Software load. The reports shall contain aforementioned
<PAGE>

       information for all current and previous releases of the Products, and
       clearly indicate for both Hardware and Software:

       a)    backward and forward compatibility;

       b)    upgradability from any release to any other release;

       c)    the current Product releases.

4.     From the date the Products will have successfully passed the Acceptance
       Program in accordance with Section 4 of the Agreement, Seller shall
       provide to Nortel's Product Brand Manager a monthly "General Business"
       report which includes the following information:

       a)    Number of Products (on a per PEC level) delivered to Nortel in
             the previous month.

       b)    Total business in dollars on a per PEC level delivered to Nortel
             in the previous month.

       c)    Number of Products (on a per PEC level) delivered year to date to
             Nortel.

       d)    Total business in dollars on a per PEC level delivered year to
             date to Nortel.

       e)    Number of Products (on a per PEC level) delivered to date to
             Nortel.

       f)    Total business in dollars on a per PEC level delivered to date to
             Nortel.

       g)    Total number of shipments that were missed or delivered short by
             Seller in the previous month.

       h)    Price in effect on a per PEC level in the previous and current
             months.

       i)    Prices paid for Nortel proprietary components in the last month.

       j)    Total number of PRS and CSR raised in the previous month against
             the Products and a summary of each problem.

       k)    Total number of calls received from the Nortel Customer Service
             center in the previous month.

5.     In addition to the above, Nortel may, from time to time, request that
       Seller provides detailed Unit Failure Analysis and Component Failure
       Analysis reports.
<PAGE>

                                   EXHIBIT G
                                   ---------
                              Change Notification
                              -------------------
                                   (Example)
<TABLE>
<CAPTION>
<S>                                         <C>
-----------------------------------------------------------------------------------------------
1.  SELLER INFORMATION:                     |2. PRODUCT CHANGE NOTICE:
                        |               1997xxxx
                                                |  ISSUE:  01
                                                          |
-----------------------------------------------------------------------------------------------
3.  ISSUE DATE:    |4. PRODUCT IDENTIFICATION:
           | MAJOR SYSTEM:
           | SUB SYSTEM  :
           | HWARE: ?  FWARE: ?  SWARE: ?  PLUGIN: ?
                     |
-----------------------------------------------------------------------------------------------
5.  NEW PROD  RLSE |7. NEW CLEI CODE |6. OLD PROD  RLSE |8. OLD CLEI CODE
   NTxxxxxx  tbd | tbd   |  NTxxxxxx      xx |  xxxxxxxxx
                    |                |                  |
-----------------------------------------------------------------------------------------------
9.  ASSOCIATED PRODUCTS OR CHANGES AFFECTED:

-----------------------------------------------------------------------------------------------
10. DRAWING NUMBER:            |11. CHANGE CLASSIFICATION:
   ADxxxxxx             |  A/AC/B.....
                                        |
-----------------------------------------------------------------------------------------------
12. CLASSIFICATION SUBSTANTIATION:

________________________________________________________________________________
13. REASON FOR CHANGE:

________________________________________________________________________________
14. DESCRIPTION OF CHANGE:

    VERIFICATION PROCEDURES:


    BACKOUT PROCEDURES:

-----------------------------------------------------------------------------------------------
</TABLE>
<PAGE>

<TABLE>
<CAPTION>
<S>                                         <C>
-----------------------------------------------------------------------------------------------
15. EFFECT OF CHANGE:
    Enhanced features and easier install ability.
    SAFETY HAZARD: ?  FIRE HAZARD: ?   SRVC AFFCTG: ?  TRANS AFFCTG: ?
    MNTNCE AFFCTG: ?  RELIA AFFCTG: ?  POWR AFFCTG: ?  TRAF  AFFCTG: ?
-----------------------------------------------------------------------------------------------
16. MATERIAL AFFECTED:

-----------------------------------------------------------------------------------------------
17. DOCUMENTATION AFFECTED:

-----------------------------------------------------------------------------------------------
18. IMPLEMENTATION DATE:       |19. CHANGE COMPLETION DATE:
    MM/DD/YY        |  N/A

-----------------------------------------------------------------------------------------------
20. MODIFICATION LOCATION:
  N/A
  TRIALED: N (Field Lab Na)
-----------------------------------------------------------------------------------------------
21. INSTALLATION HOURS AND MATERIAL COST:
  HOURS: N/A
  COST : N/A
-----------------------------------------------------------------------------------------------
22. LOCATION AND QUANTITY OF EQUIPMENT:
  N/A
-----------------------------------------------------------------------------------------------
23. ATTACHMENTS:
  None
-----------------------------------------------------------------------------------------------
24. COMMENTS:

</TABLE>
<PAGE>

                                   EXHIBIT H
                                   ---------


       [*]

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

                                   EXHIBIT I

                                      RUS

                             DEBARMENT CERTIFICATE

                                  S A M P L E


  CERTIFICATION REGARDING DEBARMENT, SUSPENSION, INELIGIBILITY AND VOLUNTARY
                  EXCLUSION - LOWER TIER COVERED TRANSACTIONS



This certification is required by the regulations implementing Executive Order
12549, Debarment and Suspension, 7 CFR Part 3017, Section 3017.510,
Participants' responsibilities.  The regulations were published as Part IV of
the January 30, 1989, Federal Register (pages 4722-4733).

(BEFORE COMPLETING CERTIFICATION, READ INSTRUCTIONS ON REVERSE)

(1)    The prospective lower tier participant certifies, by submission of this
proposal, that neither it nor its principals is presently debarred, suspended,
proposed for debarment, declared ineligible, or voluntarily excluded from
participation in this transaction by any Federal department or agency.

(2)    Where the prospective lower tier participant is unable to certify to any
of the statements in this certification, such prospective participant shall
attach an explanation to this proposal.


Organization Name                       PR/Award Number or Project Name



Name and Title of Authorized Representative



Signature                               Date
<PAGE>

Instructions For Certification

1.     By signing and submitting this form, the prospective lower tier
participant is providing the certification set out on the reverse side in
accordance with these instructions.

2.     The certification in this clause is a material representation of fact
upon which reliance was placed when this transaction was entered into. If it is
later determined that the prospective lower tier participant knowingly rendered
an erroneous certification, in addition to other remedies available to the
Federal Government, the department or agency with which this transaction
originated may pursue available remedies, including suspension and/or debarment.

3.     The prospective lower tier participant shall provide immediate written
notice to the person to whom this proposal is submitted if at any time the
prospective lower tier participant learns that its certification was erroneous
when submitted or has become erroneous by reason of changed circumstances.

4.     The terms "covered transaction", "debarred", "suspended", "ineligible",
"lower tier covered transaction", "participant", "person", "primary covered
transaction", "principal", "proposal", and "voluntarily excluded", as used in
this clause, have the meanings set out in the Definitions and Coverage sections
of rules implementing Executive Order 12549.  You may contact the person to
which this proposal is submitted for assistance in obtaining a copy of those
regulations.

5.     The prospective lower tier participant agrees by submitting this form
that, should the proposed covered transaction be entered into, it shall not
knowingly enter into any lower tier covered transaction with a person who is
debarred, suspended, declared ineligible, or voluntarily excluded from
participation in this covered transaction, unless authorized by the department
or agency with which this transaction originated.

6.     The prospective lower tier participant further agrees by submitting this
form that it will include this clause titled "Certification Regarding Debarment,
Suspension, Ineligibility and Voluntary Exclusion - Lower Tier Covered
Transactions", without modification, in all lower tier covered transactions and
in all solicitations for lower tier covered transactions.

7.     A participant in a covered transaction may rely upon a certification of a
prospective participant in a lower tier covered transaction that it is not
debarred, suspended, ineligible, or voluntarily excluded from the covered
transaction, unless it knows that the certification is erroneous.  A participant
may decide the method and frequency by which it determines the eligibility of
its principals.  Each participant may, but is not required to, check the Non-
procurement List.

8.     Nothing contained in the foregoing shall be construed to require
establishment of a system of records in order to render in good faith the
certification required by this clause.  The knowledge and information of a
participant is not required to exceed that which is normally possessed by a
prudent person in the ordinary course of business dealings.

9.     Except for transactions authorized under paragraph 5 of these
instructions, if a participant in a covered transaction knowingly enters into a
lower tier covered transaction with a person who is suspended, debarred,
ineligible, or voluntarily excluded from participation in this transaction, in
addition
<PAGE>

to other remedies available to the Federal Government, the department or agency
with which this transaction originated may pursue available remedies, including
suspension and/or debarment.
<PAGE>

                                   EXHIBIT J

               NORTH AMERICAN FREE TRADE AGREEMENT - PROCEDURES


1.1    Seller shall perform all administrative actions required to qualify
Products and maintain qualification for preferential treatment under the rules
of any applicable trade treaty between Canada, USA and Mexico including, without
limitation, the North American Free Trade Agreement ("NAFTA").  If a Product
qualifies under NAFTA, Seller shall prepare and distribute a NAFTA Exporter's
Certificate of Origin according to Sections 1.2 and 1.3 below, whichever
applies, and any other documents required. Seller shall respond to NAFTA
Exporter's Certificate of Origin questionnaires and assist each Nortel Company
in resolving any Product eligibility issues.  Seller alone shall bear
responsibility for all penalties and costs resulting from a NAFTA Exporter's
Certificate of Origin subsequently being determined to be invalid.

1.2    If a NAFTA Exporter's Certificate of Origin is prepared for each
shipment, Seller shall (a) retain the original NAFTA Exporter's Certificate of
Origin in Seller's files with appropriate backup documentation, (b) attach a
copy of the Exporter's Certificate of Origin to the customs/shipping documents
for the qualifying Product, and (c) mark these customs/shipping documents with
the legend: "Copy of the NAFTA Exporter's Certificate of Origin attached."

1.3    If a blanket NAFTA Exporter's Certificate of Origin is prepared, Seller
shall: (a) retain the original NAFTA Exporter's Certificate of Origin in
Seller's files with appropriate backup documentation, (b) mark the
customs/shipping documents for the qualifying Product with the legend: "Copy of
blanket NAFTA Exporter's Certificate of Origin on file at Nortel customs offices
in Milton, Ontario (Canada) and in Tonawanda, NY (USA)," and (c) mail copies of
the blanket NAFTA Exporter's Certificate of Origin to the following offices:

      Canada:                                   USA:
      Nortel Networks Corp.                     Nortel Networks Inc.
      Dept. 1560                                77 Oriskany Drive
      901 Steeles Avenue                        Tonawanda, NY, 14150
      Milton, Ontario, Canada  L9T 4B6          USA
<PAGE>

                                   EXHIBIT K

                                    NOTICES



           Chorum Technologies
           1303 E. Arapaho Road,
           Richardson, TX, 75081
           Attention: Vice President of Sales
           Facsimile No:
                        --------------------------------

And

           Gunderson Dettmer, LLP
           2700 Via Fortnua, Suite 300
           Austin, Texas 78746
           Attn:  Kirk Lundburg

           Facsimile No: 512/732-0081



NORTEL:    Nortel Networks Limited
           8200 Dixie Road, Suite 100
           Brampton, Ontario
           Canada L6T 5P6

           Attention: Vice-President and Deputy General Counsel
           Facsimile No: (905) 863-8425

     and:  Nortel Networks Limited
           9300 Trans Canada Highway
           St. Laurent, QC
           Canada  H4S 1K5

           Attention: Director, Purchasing and Component Engineering
           Facsimile No: (514) 818-3222
<PAGE>

                                   COVENANT


[*]

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

                                AMENDMENT #1 TO
                                      THE
                             OEM PURCHASE AND SALE
                                   AGREEMENT
                                BY AND BETWEEN
                                NORTEL NETWORKS
                                      AND
                              CHORUM TECHNOLOGIES


This amendment (the "Amendment") is made this 12th day of October, 2000 (the
"Effective Date") by and between Nortel Networks, Ltd., having an office at 8200
Dixie Road, Brampton, Ontario L6T 5P6 ("Nortel") and Chorum Technologies, Inc.
("Seller") having an office at 1303 E. Arapaho Road, Richardson, Texas 75081.

     Whereas, Nortel and Seller entered into an OEM Purchase and Sale Agreement,
effective as of 1 January 2000 (the "OEM Agreement"), and,

     Whereas, the parties desire that this Amendment revise the OEM Agreement.

Now therefore, for good and valuable consideration, the receipt and sufficiency
of which the parties acknowledge, the parties hereby amend the OEM Agreement as
follows:

1.   Insert the following as Section 8.5.6:

     [*]

All capitalized terms herein will have the meaning set forth in the OEM
Agreement.  Except as specifically provided above, the OEM Agreement shall
remain in full force and effect without modification.

THE REST OF THIS PAGE IS INTENTIONALLY LEFT BLANK; THE NEXT PAGE IS THE
SIGNATURE PAGE.

* Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.
<PAGE>

IN WITNESS WHEREOF, the Parties hereto have executed this Amendment #1 on the
day and year last written below.

CHORUM TECHNOLOGIES INCORPORATED        NORTEL NETWORKS LIMITED

By:                                     By:
   ----------------------------            ----------------------------
        (Signature)                           (Signature)
Name:                                   Name:
     --------------------------              --------------------------

Title:                                  Title:
      --------------------------              -------------------------
        (Print)                               (Print)

Date:                                   Date:
     ---------------------------             --------------------------