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                                                                  EXHIBIT 610.01
                                LICENSE AGREEMENT

MEMORANDUM OF AGREEMENT made and entered into as of the 24th day of January,
1997 ("Effective Date").

BY AND BETWEEN:            NORTHERN TELECOM LIMITED,
                           a corporation duly incorporated under the laws of
                           Canada, having an office at 8200 Dixie Road,
                           Brampton, Ontario, Canada L6T 5P6, on behalf of
                           itself and its Subsidiaries and Affiliates

                           (hereinafter called "Northern Telecom")

AND:                       APPLIED DIGITAL ACCESS, INC.
                           a  corporation  duly  incorporated  under the laws of
                           California  and  having an  office  at 9855  Scranton
                           Road, San Diego, California, U.S.A. 92121

                           (hereinafter called the "licensee")

WHEREAS Northern Telecom designs, produces and markets telecommunications
systems and is in possession of certain proprietary rights in the technology
related to such systems; and

WHEREAS Northern Telecom and Licensee have previously entered into a license
agreement for rights in respect of certain of such systems and technology; and

WHEREAS Licensee wishes to obtain further rights in respect of such systems and
technology; and

WHEREAS each Party is prepared to grant such licenses and enter into such
obligations, as hereinafter set forth.

NOW THEREFORE THIS AGREEMENT WITNESSETH THAT, IN CONSIDERATION OF THE MUTUAL
PROMISES HEREINAFTER SET FORTH, THE PARTIES AGREE AS FOLLOWS:


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                                    ARTICLE 1
                                   DEFINITIONS

As used herein, unless otherwise defined;

(a)     "Affiliate" shall mean a corporation or company which a Party hereto
        effectively controls, directly or indirectly, other than a Subsidiary,
        through the ownership or control of shares in the corporation or
        company;

(b)     "Authorized Products" shall mean all products which are developed
        byLicensee pursuant to the licenses granted in this Agreement;

(c)     "Copyrights" shall mean all copyrights owned or controlled byNorthern
        Telecom or its Subsidiaries or Affiliates in existence at anytime in any
        or all countries of the world and first existing prior to orduring the
        tern of this Agreement;

(d)     "DSS lI Product" shall mean the DSS II software product which is
        comprised of software proprietary to BC TEL, Microtel Limited and
        Northern Telecom;

(e)     "DSS II Licensed Information" shall mean those items of information and
        all source code, object code, design documentation, Northern Telecom's
        customer product documentation (including training and operations),
        installation and maintenance documentation marketing materials developed
        for general use, test specifications, Northern Telecom proprietary
        utilities and tools, command files for software development and testing,
        and everything currently used by Northern Telecom at the Effective Date
        to develop, modify and enhance the DSS II Product to the extent
        available in accordance with Article 3 hereof;

(f)     "Enhancements" shall mean any minor extensions of the features and/or
        capabilities which are contained in the DSS II licensed Information as
        it exists as of the Effective Date of this Agreement;

(g)     "Gross Sales" shall mean the proceeds paid to Licensee upon the
        sublicensing of Authorized Products or of DSS II Licensed Information,
        as well as engineering and installation related thereto, whether
        composing a lump sum and/or periodic payments; provided that Gross Sales
        shall not include (i) separately itemized taxes, support service or



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        maintenance fees, insurance, interest charges on financing provided by
        Licensee to its customers and transportation costs, actually paid by
        Licensee's customers; or (ii) any refunds for returns.

(h)     "Intellectual Property" shall mean the aggregate of Patents, Copyrights
        and Maskworks, trade secrets and know-how which relates in any way to
        DSS II Licensed Information and Authorized Products;

(i)     "Joint Venture" shall mean a joint venture company which is a
        cooperative business enterprise formed between Northern Telecom and
        other autonomous entities to address more effectively certain mutual
        business interests and opportunities.

(j)     "Manufacturing Licensee" shall mean a third party entity which has
        entered into an agreement with Northern Telecom to manufacture, in
        modified or unmodified form, Northern Telecom products and directly or
        indirectly through distributors, to sublicense and distribute Northern
        Telecom products under Northern Telecom or the Manufacturing Licensee's
        own brand name.

(k)     "Maskworks" shall mean all rights in semiconductor topology owned or
        controlled by Northern Telecom or its Subsidiaries or Affiliates similar
        to those defined in the Semiconductor Chip Protection Act of 1984 (U.S.A
        ) in existence at any time in any or all countries of the world and
        first existing prior to or during the term of this Agreement;

(1)     "Modifications" shall mean any minor changes such as, but not limited
        to, bug fixes, to the features and/or capabilities of the DSS lI
        Licensed Information as it exists as of the Effective Date of this
        Agreement;

(m)     "MOU" shall mean the Memorandum of Understanding between Northern
        Telecorn and Licensee, executed on even date to this Agreement,
        concerning the sale of the DSS II business to Licensee;

(n)     "Patents" shall mean all patents (including utility models but excluding
        design registration and design patents) owned or controlled by Northern
        Telecom or its Subsidiaries or Affiliates issued at any time in any or
        all countries of the world on applications having effective filing dates
        prior to the expiration or termination of this Agreement, including all
        continuations' continuations-in part, divisionals, reissues, additions,
        reexaminations and extensions with respect to any of the foregoing;

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(o)     "Permitted Customers" shall mean GTE and BC TEL;

(p)     "Subsidiary" shall mean a corporation or company in which a party hereto
        effectively owns or controls, and continues to own or control, directly
        or indirectly, more than fifty percent (50%) of the voting stock or
        shares;

                                    ARTICLE 2

                                 GRANT OF RIGHTS

Northern Telecom, to the extent of its legal right so to do, and provided that
Northern Telecom Limited and ADA enter into an agreement for the sale of the DSS
II business as contemplated in the MOU, will grant, subject to the terms and
conditions of this Agreement, to Licensee and its Subsidiaries and Affiliates,
for the period from the execution of this Agreement to the closing date of the
actual sale of the DSS II business as contemplated in the MOU, a personal,
non-transferable, non-exclusive, non-assignable, indivisible right;

(a)     to use and modify and have modified the DSS II Licensed Information, and
        any Enhancements and Modifications thereto licensed hereunder, to
        develop Authorized Products for Permitted Customers only;

(b)     to sublicense Authorized Products to Permitted Customers only, pursuant
        to a valid sublicense agreement containing substantially the terms set
        forth in Schedule "B";

(c)     to grant sublicenses to the DSS II licensed Information In object code
        version only, to Permitted Customers only, pursuant to a valid
        sublicense agreement containing substantially the terms set forth in
        Schedule "B";

(d)     to grant, to Permitted Customers only, provided that such Permitted
        Customers are validly sublicensed as set out herein, the right pursuant
        to an escrow agreement, if the licensee,

        (i) becomes insolvent or files an assignment in bankruptcy or fails to
        have dismissed any petition seeking to have it declared bankrupt when 30
        days after the filing thereof, or

        (ii) after using its best efforts to support Authorized Products, ceases
        all support of Authorized Products, 



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        to have access to and to use the source code version of the DSS II
        Licensed Information solely for internal use to support the Authorized
        Products; and

(e)     under Intellectual Property, but only to the extent necessary to enable
        the exercise of the rights granted In the immediately preceding
        subparagraphs.

The aforesaid rights shall include the right to communicate to Permitted
Customers purchasing the Authorized Products permitted hereunder such portions
of the DSS II Licensed Information as are reasonably needed by such Permitted
Customers for the use of the Authorized Products; provided, however, that, to
the extent that proprietary information is being communicated, the recipients of
the DSS lI Licensed Information be advised by Licensee in writing at the tine,
or before such communication, that proprietary information is being communicated
and that such information is to be kept confidential and not used except as
expressly permitted in writing and provided that such recipients undertake such
obligations of confidentiality and restricted use in writing.

For greater certainty, Licensee shall have no right to use the DSS lI Licensed
Information other than to develop Authorized Products for Permitted Customers
only, and as set forth in the immediately preceding paragraph. Nothing herein
shall be interpreted so as to restrict any rights or licenses granted to
Licensee pursuant to the License Agreement between Licensee and Northern Telecom
dated 15 July, 1996.

Licensee shall comply with all applicable governmental legislation or
regulations imposing restrictions on the export of products.

Licensee grants to Northern Telecom and its Subsidiaries, Manufacturing
Licensees and Joint Ventures a personal, non-transferable, non-assignable,
(except as provided in this Agreement) indivisible, world-wide right to use all
Enhancements and Modifications which Licensee may develop or have developed
during the term of this Agreement in connection with the use of the DSS II
Licensed Information. Northern Telecom grants to Licensee and its Subsidiaries
and Affiliates a personal, non-transferable, non-assignable, indivisible right
to use all Enhancements and Modifications which Northern Telecorn may develop or
have developed during the term of this Agreement in connection win the use of
the DSS II Licensed Information.




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Within Thirty (30) days of the end of each calendar quarter, each party shall
provide the other with a copy of all Enhancements and Modifications developed
during such preceding quarter together with all applicable documentation, or, if
applicable, written notice that no new Enhancements or Modifications have been
developed during such preceding quarter.

In the event that prior to the actual closing date of the sale of the DSS II
business as contemplated in the MOU, and provided that a Permitted Customer
wishes to enter into an agreement with Licensee which is dependent on rights in
the DSS II Information, then Northern Telecom and Licensee will negotiate in
good faith the terms of a license which, to the extent of Northern Telecom's
legal right so to do, grants to Licensee the rights necessary to complete such
agreement with such Permitted Customer. Without limiting the generality of the
foregoing, such a license between Northern Telecom and ADA shall include
applicable payments and/or royalties as well as providing for reduced commitment
by Nortel for ADA research and development capabilities and resources as set
form under the Master Agreement between Northern Telecom and Licensee dated 15
July, 1996.

                                    ARTICLE 3

                     FURNISHING DSS II LICENSED INFORMATION

Northern Telecom shall, to the extent of its legal right so to do, promptly
furnish to Licensee the DSS II Licensed Information.

Northern Telecom shall only be obliged to provide DSS II Licensed Information
available to it or its Subsidiaries, and shall not be obligated to obtain,
develop or produce, except as expressly set forth herein, any new or unavailable
DSS II Licensed Information. Northern Telecom shall supply the DSS II Licensed
Information as soon as reasonably possible after execution of this Agreement and
receipt from Licensee of the payment set forth in the first paragraph of Article
6 and substantially complete such supply within ninety (90) days therefrom.

DSS II Licensed Information provided hereunder shall be deemed delivered upon
delivery to the common carrier chosen by Northern Telecom, at the relevant
facility of Northern Telecom or upon sending by Northern Telecom if such DSS II
Licensed Information is delivered by electronic means.

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That portion of the DSS II Licensed Information provided by Northern Telecom to
Licensee pursuant to a prior confidentiality or non-disclosure agreement shall
be considered provided pursuant solely to this Agreement and subject only to the
terms and conditions hereof.

                                    ARTICLE 4

                REVIEW OF AUTJORIZE PRODUCTS BY NORTHERN TELECOM

Licensee shall advise Northern Telecom, in writing of each new release of
Authorized Products developed during the term of this Agreement and, at Northern
Telecom's request, provide suitable prototype and commercial versions of such
Authorized Products for a period not to exceed three (3) business days solely to
allow Northern Telecom to test such products. Authorized Products shall be
returned to Licensee. Northern Telecom shall, test the Authorized Products on
Northern Telecom's premises and at Northern Telecom's expense.

Licensee shall provide, free of charge, such reasonable assistance of its
qualified technical personnel as may be requested by Northern Telecom to assist
in carrying out such testing.

Northern Telecom shall provide to Licensee the results of such testing, and may,
in its sole discretion, provide to Licensee comments and advice thereon.

                                    ARTICLE 5

                              TECHNICAL ASSISTANCE

During the term of this Agreement, Northern Telecom shall make available to
Licensee, to the extent contemplated in the immediately following paragraphs,
upon the latter's request, technical assistance to facilitate the use of the DSS
II Licensed Information provided hereunder for the exercise of the rights
granted herein.

Technical assistance provided hereunder by Northern Telecom shall be provided as
reasonably required, under Northern Telecom's standard terms and conditions,
including Northern Telecom's then-current per diem rates therefor plus expenses.

Technical assistance provided hereunder shall be limited to that which is
reasonable under the circumstances and shall be scheduled by Northern 

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Telecom to serve the needs of Licensee, but not so as to inconvenience, or place
excessive demands upon, the operations of Northern Telecom, or its Subsidiaries
or Affiliates. In determining what shall constitute a reasonable amount of
support under the circumstances, consideration shall be also be given to the
support provided by Northern Telecom to Licensee pursuant to the License
Agreement between the Parties dated 15 July, 1996. Technical assistance shall
include both consulting technical services of Northern Telecom and visits of
Northern Telecom personnel to Licensee's facilities.

Technical assistance provided by Northern Telecom prior to the commencement of
this Agreement and related to the subject matter hereof shall be considered
provided pursuant to this Agreement and subject only to the terms and conditions
hereof.

                                    ARTICLE 6

                                     PAYMENT

In the event that pursuant to Article 2, Northern Telecom and Licensee enter
into negotiations in respect of a license agreement for rights in the DSS II
Information, Northern Telecom and Licensee shall negotiate in good faith a value
for such rights. In the event that Northern Telecom and Licensee execute a
license agreement as contemplated under Article 2, the value of the rights, as
negotiated by Northern Telecom and Licensee, shall be included in the sale price
of the DSS II business.

If the amount that a third party shall pay to Licensee for the Authorized
Products and associated engineering and installation cannot be determined at the
time that Licensee grants a license to such third party because such amount is
not separately identified, Licensee shall pay to Northern Telecom an amount
determined as set out below:

(i)     Licensee shall establish a list price for the Authorized Product for the
        particular third party customer; and

(ii)    Licensee shall then determine a discount percentage to be applied
        against such price based upon current market practice and the average
        discount percentage applied to the previous five (5) licenses granted to
        the Authorized Product for which the licensee most closely approximates
        such license with respect to the size and functionality of the system
        being licensed; provided however, that suds average shall include all
        prior licenses of the Authorized Product, if five (5) or fewer of such
        prior licenses have been granted at that time.



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                                    ARTICLE 7

                             RECORDS AND REMITTANCES

Licensee shall keep clear and accurate records with respect to the Authorized
Product and the DSS II licensed Information. Northern Telecom shall have the
right through its internal auditing experts, to examine and audit, during normal
hours, annually (or at less frequent intervals) all such records and such other
records and accounts as may under recognized accounting practices contain
information bearing upon the amounts payable to it under this Agreement. Prompt
adjustment shall be made by the proper party to compensate for any errors or
omissions disclosed by such examination or audit. Neither such right to examine
and audit, nor the right to receive such adjustments, shall be affected by
statements to the contrary appearing on cheques or otherwise, unless any such
right is expressly waived by the party having such right. Licensee shall furnish
whatever additional information Northern Telecom may reasonably prescribe from
time to time to enable Northern Telecom to ascertain whether the Authorized
Product or DSS II Licensed Information sublicensed is subject to the payment of
royalties hereunder and the amount payable thereon.

Within sixty (45) days following the end of each quarterly period ending on
March 31, June 30, September 30 or December 31, commencing with the first
quarterly period after the execution date of this Agreement and continuing
thereafter until all royalties payable hereunder shall have been reported and
paid, Licensee shall furnish to Northern Telecorn a statement, in a form
acceptable to Northern Telecom, certified by an authorized official of Licensee,
recording all Authorized Products or DSS II Licensed Information sublicensed
during such quarterly period, the Gross Sales and the amount of royalties
payable thereon. If no Authorized Products or DSS II licensed Information have
been sublicensed, that fact shall be shown on such statement.

On the last day of each quarterly period, Licensee shall pay to Northern Telecom
the royalty applicable to all amounts received in such quarter.

All payments to be made by Licensee to Northern Telecom shall be made in United
States Dollars at Northern Telecom's address as shown in Article 13 hereof, Or
at such other address as Northern Telecom shall have specified by written
notice.

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Licensee shall pay all taxes imposed a result of the existence or operation of
this Agreement including, but not restricted to, registration fees, remittance
fees, stamp taxes, sales, value added or use imposed with respect to the
granting or transfer of rights hereunder or the payment or receipt of fees
hereunder and any tax which Licensee shall be required to withhold or deduct
from fees or other payments to Northern Telecom except any tax on income imposed
on Northern Telecom.

Payments when provided for in this Agreement shall, when overdue, bear interest
at a monthly rate of one and one-half percent (1.5%) or an annual rate of
eighteen percent (18%).

                                    ARTICLE 8

                            CONFIDENTIAL INFORMATION

Any information or materials (including DSS II Licensed Information) provided by
Northern Telecom hereunder ("Confidential Information") shall remain the
property of Northern Telecom, and the licensee shall be authorized to use such
information or materials only within the scope of the rights and licenses herein
granted.

Except as hereinafter provided, for a period of three (3) years following the
date of termination of this Agreement, Licensee shall protect Confidential
Information provided to it by use of the same care and discretion to avoid
disclosure, publication, or dissemination of such Confidential Information, as
the case may be, beyond those employees of Licensee with a need to know such
information for the purposes of this Agreement, as the Licensee employs with
similar information of its own which it does not desire to disclose, publish or
disseminate.

Information which would otherwise be classified as Confidential Information
hereunder shall not be treated as confidential, or otherwise subject to the
restrictions and obligations set forth in this Article 8, if such information:

(a)     is already in the possession of Licensee without obligation of
        confidence and is so documented;

(b)     is independently developed by licensee and is so documented;

(c)     is or becomes publicly available without breach of this Agreement,
        including DSS II Licensed Information which is made public;




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(d)     is rightfully received by Licensee from a third party without obligation
        of confidence; or

(e)     is released for disclosure by Northern Telecom with its written consent.


                                       ARTICLE 9

                                       LIABILITY

Northern Telecom makes no representations in respect to and does not warrant any
DSS II Licensed Information furnished pursuant hereto, but shall furnish such in
good faith to the best of its knowledge and ability. Without restricting the
generality of the foregoing, Northern Telecom makes no representations or
warranties as to merchantability or fitness for a particular purpose, or as to
whether or not the use of the DSS II Licensed Information supplied hereunder may
infringe any patent or other rights of any other person.

Licensee shall indemnify and save Northern Telecom harmless from any and all
claims and liabilities for damages, losses, expenses or costs (including counsel
fees and expenses) arising out of any infringement or alleged infringement by
any modification to the DSS II Licensed Information made by or on behalf of
Licensee as well as any and all claims and liabilities arising out of any
modification to the DSS II Licensed Information made by or for Licensee.

Northern Telecom represents that to the best of its knowledge there is no
conflicting claim related to the rights granted hereunder. In the event of any
suit against Licensee or its customers for any alleged infringement of any
intellectual property right or any other right of any third party arising from
the sale or sublicense of Authorized Products by licensee, Northern Telecom's
sole and only obligation and liability shall be to assist Licensee in defending
or otherwise dealing with such suit, at Licensee's expense, without incurring
any liability with respect to any such assistance.

In the event that either party becomes aware of any actual or suspected acts of
a third party that do or naught infringe Intellectual Property rights through
use of the DSS II Licensed Information, which infringement does or might affect
any Authorized Product (an "Infringement"), such party shall notify the other of
the Infringement and Northern Telecom may choose, but shall have no obligation,
to institute and prosecute any action or proceeding with respect to the
Infringement at the cost of Northern Telecom, and Northern Telecom


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shall be entitled to any and all proceeds recovered from third parties as a
result of such enforcement. Northern Telecom agrees not to take any action
inconsistent with this Agreement in the settlement of any action.

If Northern Telecom elects not to prosecute any Infringement suit, licensee may
do so at Licensee's own expense after notice to Licensee of that intention and
Licensee shall be entitled to any and all proceeds as a result of such
enforcement to the extent that such proceeds relate to infringement against
Authorized Products.

Licensee shall indemnify and save Northern Telecom harmless from any and all
claims and liabilities for damages, losses, expenses or costs (including counsel
fees and expenses) arising out of the furnishing or receipt of any technical
assistance pursuant hereto and hereby waives any claims that it might have or
might pretend to have against Northern Telecom, its employees and agents, as
well as those of its Subsidiaries and Affiliates, for or arising Tom the
provision of such assistance or information.

Notwithstanding anything else in this Article 9, Northern Telecom agrees that it
shall indemnify and save the Licensee and its Affiliates and Sublicensees
harmless with respect to any suit based on a claim that the use of the DSS II
Licensed Information or the sublicensing of the same infringes any intellectual
property right of any third party; provided that such obligation of Northern
Telecom shall apply only to the extent that Northern Telecom is indemnified by
MPR Teltech Ltd. ("MPR") pursuant to the master agreement (the "Development
Agreement") made as of December 11,1992 between MPR and Northern Telecom (as
assignee of Prism Systems Inc.) arid subject to the restrictions and releases
set form in the Development Agreement and in the DSS II development assignment
agreement made as of July 15, 1996 among MPR, ADA Canada, Inc., Northern Telecom
and BC Telecom Inc. For greater certainty, nothing in this paragraph shall
render Northern Telecom liable to Licensee in respect of a claim of infringement
for any amount in excess of the amount received by Northern Telecom from MPR in
respect of such claim of infringement.

                                   ARTICLE 10

                                  FORCE MAJEURE

Neither Party shall be in default or liable for any loss or damage resulting
from delays in performance or from failure to perform or comply with terms of
this Agreement due to any causes beyond its reasonable control during the


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continuation of such causes, which causes include but are not limited to Acts of
God or the public enemy; riots and insurrections, war, accidents, fire, strikes
and other labor difficulties (whether or not the Party is in a position to
concede to such demands), embargoes, judicial action; lack of or inability to
obtain export permits or approvals, necessary labor, materials, energy,
components or machinery; acts of civil or military authorities.

                                   ARTICLE 11

                                    DURATION

This Agreement shall commence on the above mentioned Effective Date and
terminate (save with the exception of the survivorship provisions set forth in
He final paragraph of Article 12) upon completion of a period of three (3) years
following such date. Following the expiry of this Agreement by the passage of
time, Licensee may continue to exercise the licenses granted pursuant to Article
2 as though this Agreement had continued.

                                   ARTICLE 12

                                   TERMINATION

In the event either Party shall be in breach of this Agreement or fail to
perform one or more of its material obligations under this Agreement, the other
Party may, by written notice to the Party in default, require the remedy of the
breach or the performance of the obligation and, if the Party so notified fails
to remedy or perform within sixty (60) days of He forwarding of a notice go to
do, the other Party may, by written notice, terminate this Agreement.

In the event of an enforceable decision or directive declaring invalid an
essential part of this Agreement) without which this Agreement would not have
been entered into, this Agreement may, at the option of either Party, be
terminated upon the giving of notice to the other Party. Save as before set
forth, in the event that any tern, clause, provision or condition of this
Agreement shall be similarly adjudged invalid for any reason whatsoever, such
invalidity shall not affect the validity or operation of any other term, clause,
provision or condition and such invalid term, clause, provision or condition
shall be deemed to have been deleted from this Agreement.

In the event that Licensee becomes majority owned or controlled by an entity
which is a direct competitor of Northern Telecorn, Licensee shall forthwith



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provide written notification to Northern Telecom of such change in majority
ownership or control. Within thirty (30) days of receipt of such change in
ownership or control, Northern Telecom may, in its sole discretion, elect to
terminate this Agreement and the licenses granted hereunder provided that the
acquiring entity is reasonably determined to be a direct competitor of Northern
Telecom.

In the event either Party becomes involved or is the object of bankruptcy or
insolvency proceedings, or makes an assignment for the benefit of its creditors,
or is placed in receivership or liquidation, or fails to satisfy any final
judgment rendered against it within the period so permitted, then, the over
Party may, without any delay, by written notice, terminate this Agreement.

In the event of termination of this Agreement prior to the expire of its term,
Licensee shall discontinue the exercise of the rights granted hereunder and the
use of the DSS II Licensed Information and shall pay to Northern Telecom all
amounts due hereunder.

Notwithstanding any termination hereunder, the provisions of Articles 2 and 8
related to confidentiality and non-use, and the provisions of Article 9 related
to liability shall survive the termination of this Agreement.

                                   ARTICLE 13

                                     NOTICES

Any and all notices or other information to be given by one of the Parties to
the other shall be deemed sufficiently given when forwarded by prepaid,
registered or certified first class air mail or by facsimile, telegram, telex or
hand delivery to the other Party at the following address:

If to Northern Telecom:          Northern Telecom Limited
                                 8200 Dixie Road
                                 Brampton, Ontario
                                 Canada L6T 5P6
                                 Attention: Corporate Secretary



If to Licensee:                  Applied Digital Access, Inc.
                                 9855 Scranton Road
                                 San Diego, California
                                 U.S.A. 92121
                                 Attention: President

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and such notices shall be deemed to have been received fifteen (15) business
days after mailing if forwarded by mail, and the following business day if
forwarded by facsimile, telegram, telex or hand.

The aforementioned address of either Party may be changed at any time by giving
fifteen (15) business days prior notice to the other Party in accordance with
the foregoing.

In the event of a generally-prevailing labor dispute or other situation which
will delay or impede the giving of notice by any such means, in either the
country of origin or of destination, the notice shall be given by such specified
mode as will be most reliable and expeditious and least affected by such dispute
or situation.

                                   ARTICLE 14

                                GENERAL PROVISION

Neither Party may assign all or any portion of this Agreement without the other
Party's prior written consent. Notwithstanding the foregoing, a Party may assign
and transfer this Agreement and its rights and obligations hereunder to its
parents, Affiliates or Subsidiaries. In no event shall either Party create any
contractual relation between any third party and the other.

The Parties recognize that the transfer of DSS II Licensed Information to or
from a country other than Canada or the United States of America may be subject
to the specific approval of the governments of such countries or serious
agencies thereof.

Nothing in this Agreement shall be construed as requiring Northern Telecom to
disclose technical information, or to grant rights under licenses, or to render
any technical assistance, which would violate any confidentiality undertakings
which it has towards third persons or which would violate any present or future
law or decrees of any government or governmental office or agency, and nothing
contained herein shall require the disclosure of technical information which
would increase or impose any obligations on Northern Telecom with respect to
third parties.

Nothing contained in this Agreement shall be construed as:

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(a)     requiring Northern Telecom to file any patent application, to secure any
        patent or to maintain any patent in force;

(b)     constituting a warranty or representation by Northern Telecom as to
        the validity or scope of any patent licensed hereunder;

(c)     constituting a warranty or representation bar Northern Telecom that any
        use, lease, sale or sublicense by Licensee hereunder will be free from
        infringement of patents, copyrights and other intellectual property
        rights other than those under which, and to the extent to which,
        licenses are granted hereunder;

(d)     constituting an agreement to bring or prosecute actions or suits against
        third parties for infringements;

(e)     conferring any right to use, in advertising, publicity or otherwise, any
        name, trade-name or trademark, or any contraction, abbreviation or
        simulation thereof;

(f)     conferring by implication, estoppel or otherwise upon Licensee any
        license or other right under any patent, except the licenses arid rights
        expressly granted hereunder.

Except as explicitly set forth herein, nothing contained in this Agreement shall
limit, in any manner, either Party's right to discontinue or change the design
or characteristics of any of its products (including DSS II Licensed
Information) at any time without notice and without liability.

The failure of either Party to give notice to the other Party of the breach or
non-fulfillment of any term, clause, provision or condition of this Agreement
shall not constitute a waiver thereof, nor shall the waiver of any breach or
non-fulfillment of any term, clause, provision or condition of this Agreement
constitute a waiver of any over breach or non-fulfillment of that or any other
term, clause, provision or condition of this Agreement.

All technical and other information provided or made available to Licensee prior
to the execution of this Agreement which should have been covered by the
definitions of DSS II Licensed Information or Confidential Information had it
been delivered pursuant to this Agreement shall be deepened to be DSS II
Licensed Information or Confidential Information, as the case may be, and to be
subject to the provisions of this Agreement.




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This Agreement sets forth the entire agreement and understanding between the
Parties with respect to the subject matter addressed herein and supersedes and
cancels all previous negotiations, agreements, commitments, and writings in
respect to the subject matter hereof, and neither Party hereto shall be bound by
any term, clause, provision or condition save as expressly provided in this
Agreement or as duly set forth on or subsequent to the date hereof in writing,
signed by duly authorized officers of the Parties.

Nothing in this Agreement shall be construed as establishing or implying an,
partnership between the Parties hereto, and nothing in this Agreement shall be
deemed to constitute either of the Parties hereto as the agent of the other
Party or authorize either Party to incur any expenses on behalf of the other
Party or to commit the other Party in any way whatsoever, without obtaining the
other Party's prior written consent.

The specific terns and conditions of this Agreement shall be held in confidence
by both Parties and only disclosed as may be agreed by both Parties, which
agreement shall not be unreasonably withheld by either Party. Notwithstanding
the foregoing, or paragraph (e) above, either Party may make public statements,
issue publicity or media releases, or make other disclosures, revealing the
existence of this Agreement, and the general relationship of the Parties
hereunder, without the prior approval of the other Party.

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

IN WITNESS WHEREAS, the Parties hereto have executed this Agreement on the date
first above mentioned.

NORTHERN TELECOM LIMITED               APPLIED DIGITAL ACCESS, INC.

Per. /s/ DAVID ARCHIBALD               Per. /s/ PETER P. SAVAGE
    ------------------------------         -------------------------------
    David Archibald                        Peter P. Savage
    Vice President and                     President and Chief Executive Officer
    Deputy General Counsel

Dated: February 7, 1997                Dated: February 7, 1997
      ----------------------------           -----------------------------


Per. /s/ D. J. NOBLE                   Per. /s/ JAMES L. KEEFE
    ------------------------------         -------------------------------
    D.J. Noble                             James L. Keefe
    Assistant Secretary                    Chief Financial Officer

Dated: February 7, 1997                Dated: February 7, 1997
      ----------------------------           -----------------------------

17
   18






                                  SCHEDULE "A"

                           DSS II LICENSED INFORMATION




   19




                                  SCHEDULE "B"

                               SUBLICENSING TERMS

 Sublicense agreements shall include terms and conditions substantially similar
to the following:

1.      restrict use of the Authorized Products or DSS II Licensed Information
        to object code form only;

2.      prohibit causing or permitting the reverse engineering, disassembly or
        Recompilation of the Authorized Products or DSS II Licensed
        Information except to the extent permitted by law or required to obtain
        interoperability with other independently created software programs;

3.      prohibit title to the Authorized Products or DSS II Licensed Information
        from passing to the end user;

4.      disclaim Northern Telecom liability for any damages, whether direct,
        indirect, incidental or consequential arising from the use of the
        Authorized Products or DSS IT Licensed Information; and

5.      require the end user, at the termination of the sublicense, to
        discontinue use and destroy or return to Licensor the Authorized
        Products or DSS II Licensed Information, associated documentation and
        all archival or other copies of the Authorized Products or DSS II
        licensed Information.

6       in any sublicense to United States Government end users, include the
        following on all copies of Authorized Products distributed to United
        States Government end users:

        This software is provided with RESTRICTED Rights. Use, Duplication, or
        Disclosure by the U.S. Government is subject to restrictions as set
        forth in subparagraph (c) (1) (ii) of The Rights in Technical Data and
        Computer Software clause at DFARS 252.227-7013 or subparagraphs (c) (1)
        and (2) of the Commercial Computer Software Restricted Rights at 48 CFR
        52.227-19, or successor legislation, as applicable.
        Contractor/Manufacturer is Northern Telecom Limited, 100 Dixie Road,
        Brampton, Ontario Canada L6T 5P6


   20




7.      End user shall comply with all applicable governmental legislation or
        regulations imposing restrictions on the export of products.



   21



                                         INDEX


ARTICLE                      TITLE
- -------                      -----
                            
     1                       DEFINITIONS

     2                       GRANT OF RIGHTS

     3                       FURNISHING OF DSS II LICENSED COMMON

     4                       REVIEW OF AUTHORIZED PRODUCTS BY NORTHERN TELECOM

     5                       TECHNICAL ASSISTANCE

     6                       PAYMENT

     7                       RECORDS AND REMITTANCES

     8                       CONFIDENTIAL INFORMATION

     9                       LIABILITY

     10                      FORCE EJECT

     11                      DURATION

     12                      FORCE MAJEURE

     13                      NOTICES

     14                      GENERAL PROVISIONS


SCHEDULE  "A"  DSS II LICENSED INFORMATION
SCHEDULE  "B"  SUBLICENSING TERMS