Exhibit 4.01 
                                                                                
                          REGISTRATION RIGHTS AGREEMENT


         This  Registration  Rights  Agreement,  dated as of April 3,  1998 (the
"Agreement"),  is made and entered into by and between Digital Link Corporation,
a  California   corporation   (the   "Company")  and  Semaphore   Communications
Corporation, a Delaware corporation ("Semaphore").

         WHEREAS,  Semaphore  has  been  issued  291,182  shares  of  the  
Company's outstanding Common Stock;

         NOW, THEREFORE,  in consideration of the mutual promises and agreements
hereinafter  set forth,  and for other valuable  consideration,  the Company and
Semaphore agree as follows:

         1. Definitions. The Company's Common Stock, no par value, and any other
securities of the Company  convertible  into or  exchangeable  for the Company's
Common Stock are  hereinafter  referred to as the "Common Stock" and the 291,182
shares of Common Stock  beneficially  owned by the  Stockholders are hereinafter
referred to as the "Shares." The term  "Registrable  Securities"  means: (i) the
Shares;  and (ii) any  shares of  Company  Common  Stock that may be issued as a
dividend  or other  distribution  (including  without  limitation  shares of the
Company's  Common  Stock  issued in a  subdivision  and  split of the  Company's
outstanding Common Stock) with respect to, or in exchange for, or in replacement
of,  shares of the  Company's  Common Stock  described in clause (i) above or in
this clause  (ii);  excluding  in all cases,  however,  from the  definition  of
"Registrable Securities" any such shares that are: (w) registered under the 1933
Act other than  pursuant  to a  registration  statement  filed  pursuant to this
Agreement;  (x) sold by a person in a  transaction  in which  rights  under this
Agreement  with respect to such shares are not assigned in  accordance  with the
terms of this  Agreement;  (y) sold pursuant to a registration  statement  filed
pursuant to this Agreement;  or (z) sold pursuant to Rule 144 promulgated  under
the 1933 Act or otherwise  sold to the public.  For purposes of this  Agreement,
the terms  "beneficial  ownership,"  "person"  and  "affiliate,"  shall have the
meanings  ascribed to such terms in Rules  12b-2 and 13d-3 under the  Securities
Exchange Act of 1934 (the "1934 Act").  Each of the terms  "Securities  Act" and
"1933 Act" means the  Securities  Act of 1933, as amended.  The term "SEC" means
the Securities and Exchange Commission. Capitalized terms used but not otherwise
defined  herein shall have the meaning given to them in the Asset Sale Agreement
of even date herewith. As used herein, the term "Stockholder" and "Stockholders"
shall mean  Semaphore  or any  assignee  of record of the Shares to whom  rights
under this Agreement  have been duly assigned in accordance  with the provisions
of this Agreement.

         2. Assignment of Registration  Rights.  The rights to cause the Company
to  register  Common  Stock  pursuant  to Section 4 below may be assigned by the
Stockholder only with the Company's express prior written consent,  which may be
withheld in the Company's sole discretion; provided, however, that the rights of
a Stockholder under this Agreement may be assigned without the Company's express
prior written consent:  (a) to a Permitted  Assignee (as defined below);  or (b)
(if  applicable) by will or by the laws of intestacy,  descent or  distribution,
provided that the assignee  agrees in writing to be bound by all the obligations
of the Stockholder under this Agreement. Any attempt to assign any rights of the
Stockholder  under this  Agreement  without the Company's  express prior written
consent in a situation in which such  consent is required by this Section  shall
be null and void and without effect. Subject to the foregoing restrictions,  all
rights,  covenants  and  agreements  in this  Agreement  by or on  behalf of the
parties  hereto will bind and inure to the benefit of the  respective  permitted
successors and assigns of the parties hereto.  Each of the following parties are
"Permitted  Assignees"  for  purposes  of this  Section  2:  (a) a  trust  whose
beneficiaries  consist solely of a Stockholder and such Stockholder's  immediate
family; (b) the personal  representative (such as an executor of a Stockholder's
will),  custodian or  conservator  of a  Stockholder,  in the case of the death,
bankruptcy or adjudication of incompetency of that Stockholder;  (c) partners of
a Stockholder that is a partnership,  if Registrable  Securities are distributed
pro rata, without additional consideration, to the partners; (d) stockholders of
a  Stockholder  that  is  a  corporation,  if  the  Registrable  Securities  are
distributed  to  such  stockholders;  or  (d)  immediate  family  members  of  a
Stockholder.

         3.  Termination  of Section  4. The  Company  will have no  obligations
pursuant to Section 4 of this  Agreement with respect to any Notice of Resale or
other request or requests for registration (or inclusion in a registration) made
by any Stockholder or to maintain or continue to keep effective any registration
or  registration   statement  pursuant  hereto:  (a)  after  the  expiration  or
termination of the Registration Period; (b) with respect to Section 4.3 only, if
the Company has already  effected three (3) Permitted  Windows  pursuant to this
Agreement;  (c) with respect to a particular  Stockholder  if, in the opinion of
counsel to the Company,  all such Registrable  Securities proposed to be sold by
such  Stockholder  may be sold in a three (3) month period without  registration
under  the  1933 Act  pursuant  to Rule 144  promulgated  under  the 1933 Act or
otherwise;  or (d) if all  Registrable  Securities have been registered and sold
pursuant to a registration  effected pursuant to this Agreement and/or have been
transferred in transactions in which registration rights hereunder have not been
assigned in accordance with this Agreement.

         4.       Registration Rights.

                  4.1.1 In the event that the Company  proposes to register  any
shares of Common Stock under the 1933 Act (other than for an offering  primarily
or exclusively to employees or in connection  with the acquisition of the assets
or shares  of,  or merger or  consolidation  with,  another  corporation)  and a
registration  form  is  available  for  use  which  may  also  be  used  for the
registration of the Shares held by the Stockholder (a "Piggyback Registration"),
the Company shall notify the Stockholder at least 15 days prior to the filing of
any  such  registration  form  with the SEC,  and will use its best  efforts  to
include in such  registration  all such Shares with respect to which the Company
has received  written  request for  inclusion  within 10 days after such notice.
Each such request shall specify the number of shares such Stockholder  wishes to
include in such registration statement and shall contain an undertaking from the
Stockholder  to provide all such  information  and material and to take all such
actions as may be  required  by the  Company  in order to permit the  Company to
comply with all applicable federal and state securities laws.

                  4.1.2  The  Stockholder  shall pay all  sales  commissions  or
similar selling charges with respect to Shares sold by the Stockholder  pursuant
to a Piggyback  Registration.  The Company shall pay all registration and filing
fees,  fees and expenses of compliance with federal and state  securities  laws,
printing  expenses,  messenger and delivery  expenses,  accounting  fees and the
reasonable fees and disbursements of counsel for the Company and one counsel for
the Stockholders in connection with a Piggyback Registration.

                  4.1.3  If a  Piggyback  Registration  is for  an  underwritten
offering,  then the  Company  shall so advise the  Stockholders  of  Registrable
Securities.  In such  event,  the  right of any such  Stockholder's  Registrable
Securities to be included in a registration pursuant to this Section 4.1.1 shall
be conditioned upon such  Stockholder's  participation in such  underwriting and
the inclusion of such Stockholder's  Registrable  Securities in the underwriting
to the extent provided herein.  All  Stockholders  proposing to distribute their
Registrable   Securities   through  such   underwriting   shall  enter  into  an
underwriting  agreement  in  customary  form with the  managing  underwriter  or
underwriter(s)  selected  for  such  underwriting.   Notwithstanding  any  other
provision of this Agreement,  if the managing underwriters advise the Company in
writing that in their  opinion the number of shares  requested to be included in
such Registration  exceeds the number which can be sold in such offering or will
have a material adverse effect on the price of the Common Stock to be sold, then
the Company will include in such Registration (a) first,  shares of Common Stock
the Company proposes to sell and (b) second, shares that the Stockholder and any
other stockholders which have registration rights have requested to be included,
pursuant to the terms of their applicable  registration  rights agreement,  on a
pro rata basis based on the total number of registrable  securities then held by
each such stockholder.  If any Stockholder  disapproves of the terms of any such
underwriting, such Stockholder may elect to withdraw therefrom by written notice
to the Company and the  underwriter,  delivered at least ten (10)  business days
prior to the  effective  date of the  registration  statement.  Any  Registrable
Securities  excluded or withdrawn from such  underwriting  shall be excluded and
withdrawn from the  registration.  For any Stockholder which is a partnership or
corporation,   the  partners,   retired   partners  and   shareholders  of  such
Stockholder,  or the estates and family members of any such partners and retired
partners and any trusts for the benefit of any of the foregoing persons shall be
deemed to be a single  "Stockholder," and any pro rata reduction with respect to
such  "Stockholder"  shall be based upon the aggregate amount of shares carrying
registration  rights  owned by all  entities  and  individuals  included in such
"Stockholder," as defined in this sentence.

         4.2 Reporting.  With a view to making available to the Stockholders the
benefits of certain rules and  regulations  of the SEC which may permit the sale
of the Registrable Securities to the public on Form S-3 or without registration,
after such time as a public  market  exists for the Common Stock of the Company,
the Company agrees to use its best efforts to:

                  4.2.1 At all times make and keep public information available,
as those terms are  understood  and defined in SEC Rule 144 under the Securities
Act and Item I.A.3 of Form S-3 or any similar or analogous rule or form;

                  4.2.2 File with the SEC, in a timely  manner,  all reports and
other  documents  required of the Company under the Securities Act and 1934 Act;
and

                  4.2.3  So  long  as  the   Stockholders  own  any  Registrable
Securities,  furnish to the  Stockholders  forthwith  upon  written  request:  a
written  statement  by the  Company  as to its  compliance  with  the  reporting
requirements  of said Rule 144 of the Securities Act and of the 1934 Act; a copy
of the most recent  annual or quarterly  report of the  Company;  and such other
reports and  documents as the  Stockholder  may  reasonably  request in availing
itself  of any  rule or  regulation  of the SEC  allowing  it to sell  any  such
securities without registration.

The  Company  agrees  that  upon  receiving  notice  from a  Stockholder  of its
intention  to avail  itself of benefits of Rule 144 or any similar or  analogous
rule, or of Section 4.3 below,  the Company will as soon as  practicable  comply
with the information and reporting  requirements of this Section 4.2 if, despite
the Company's best efforts to effect ongoing  compliance,  there shall have been
any failure or lapse in fulfilling the reporting and information requirements of
this Section.

         4.3      Form S-3 Registration.

                  4.3.1    Registration and Notice.

                  (a) Filing and Registration  Period. In case the Company shall
receive  from the  Stockholder  a  written  request  that the  Company  effect a
registration  on Form  S-3 and any  related  qualification  or  compliance  with
respect  to  all or a part  of the  Registrable  Securities,  then  as  soon  as
practicable thereafter,  and consistent with the requirements of applicable law,
the Company shall prepare and file with the SEC a registration statement on Form
S-3 for an  offering  to be made on a  continuous  basis  pursuant  to Rule  415
covering  all  of  the  then  outstanding  Registrable  Securities  (the  "Shelf
Registration").  The Company shall use its reasonable good faith efforts to have
such Shelf  Registration  declared  effective as soon as  practicable  after its
filing and to keep the Shelf Registration  continuously effective under the 1933
Act for a  continuous  period of time  (such  period of time  being  hereinafter
called the "Registration  Period") commencing on the date the Shelf Registration
is   declared   effective   under  the  1933  Act  by  the  SEC  (the  "Date  of
Effectiveness")  and ending on the date that is the first (1st)  anniversary  of
the Closing  (subject to Section  4.3.2(b)).  The Company  shall have no duty or
obligation to keep the Shelf  Registration (or any Subsequent  Registration,  as
defined  below)  effective  after the  expiration  of the  Registration  Period.
Accordingly,  the Stockholders  acknowledge that the Registrable Securities will
not be registered under the 1933 Act beginning one (1) year after the Closing.

                  (b)  Subsequent  Registration.  If the Shelf  Registration  is
filed  with the SEC and  becomes  effective  under the 1933  Act,  and the Shelf
Registration or a Subsequent  Registration (as defined below)  thereafter ceases
to be effective for any reason at any time during the Registration  Period, then
the Company  shall use its best efforts to obtain the prompt  withdrawal  of any
order  suspending  the  effectiveness  thereof,  and in any event shall,  within
thirty (30) days of such  cessation of  effectiveness,  file an amendment to the
Shelf Registration  seeking to obtain the withdrawal of the order suspending the
effectiveness  thereof,  or file an additional  "shelf"  registration  statement
pursuant to Rule 415 covering all of the then outstanding Registrable Securities
(a  "Subsequent  Registration").  If a  Subsequent  Registration  is filed,  the
Company shall use its best efforts to cause the  Subsequent  Registration  to be
declared  effective  as soon as  practicable  after such filing and to keep such
registration  statement continuously effective until the end of the Registration
Period.

                  (c) Supplements  and Amendments.  Subject to the provisions of
Section  4.3.1(g),  during the Registration  Period the Company shall supplement
and amend the Shelf  Registration  if, as and when required by the 1933 Act, the
rules and  regulations  promulgated  thereunder  or the  rules,  regulations  or
instructions  applicable to the  registration  form used by the Company for such
Shelf Registration.

                  (d)  Timing  and  Manner  of  Sales.  Any sale of  Registrable
Securities  pursuant to a Shelf Registration or a Subsequent  Registration under
this  Section  4.3 may be made only during a  "Permitted  Window" (as defined in
Section  4.3.1(g)  below).  In  addition,  any  sale of  Registrable  Securities
pursuant to a Shelf Registration or a Subsequent Registration under this Section
4.3 may only be made in accordance with the method or methods of distribution of
such Registrable Securities that are described in the registration statement for
the Shelf Registration (or Subsequent Registration, as applicable) and permitted
by such form of registration  statement,  which methods of distribution  will be
specified by the  Stockholders in their Notice of Resale (as defined  below).  A
Stockholder may also sell Registrable Securities in a bona fide private offering
if the  selling  Stockholder  provides  the  Company  with a written  opinion of
counsel,  reasonably satisfactory to counsel to the Company, that such offer and
sale is an exempt transaction under the 1933 Act and applicable state securities
laws,  complies with all requirements for such exemption(s) and is not made with
use of the prospectus for the Shelf Registration (or Subsequent Registration, if
applicable).  Each  Stockholder  agrees  that it will not  sell any  Registrable
Securities in any manner that would breach or violate any agreement between such
Stockholder and any third party.

                  (e) Trading  Limits;  No  Underwritings.  During any  calendar
quarter during the Registration Period, the Stockholders,  collectively, may not
sell an amount of Registrable  Securities  that, in the  aggregate,  exceeds two
percent (2%) of the outstanding  shares of Company Common Stock (as indicated in
the Company's then most recent  published  report)  without the Company's  prior
written consent. No sale of Registrable  Securities under any Shelf Registration
(or  Subsequent  Registration)  effected  pursuant  to this  Section  4.3 may be
effected  pursuant to any  underwritten  offering  without the  Company's  prior
written consent, which may be withheld in its sole and absolute discretion.

                  (f) Notice of  Resale.  Before  any  Stockholder  may make any
sale,  transfer or other  disposition of any  Registrable  Securities  under the
Shelf  Registration  (or a  Subsequent  Registration)  during  the  Registration
Period,  a Stockholder or Stockholders  who own at least twenty percent (20%) of
the then  outstanding  Registrable  Securities must first give written notice to
the  Company (a "Notice  of  Resale")  of such  Stockholder's  or  Stockholders'
present  intention to so sell,  transfer or otherwise  dispose of some or all of
such Stockholder's or Stockholders'  Registrable  Securities,  and the number of
Registrable  Securities  such  Stockholder  proposes  to so  sell,  transfer  or
otherwise  dispose  of.  In  addition,  a Notice  of Resale  shall  contain  the
information  required to be included  therein under Section 4.3.1(d) and Section
4.3.1(g).

                  (g)      Permitted Window; Sale Procedures.

                           (i) A "Permitted  Window" is a period of thirty (30) 
consecutive  calendar days commencing upon the Company's written notification to
the Stockholders in response to a Notice of Resale that the prospectus contained
in the Form S-3  registration  statement filed pursuant to Section 4.3.1 of this
Agreement is available to be used for resales of Registrable Securities pursuant
to the Shelf Registration (or a Subsequent Registration, as applicable).

                           (ii) Before a Stockholder can make a sale of any 
Registrable Securities,  and in order to cause a Permitted Window to commence, a
Stockholder or Stockholders who own(s) at least twenty percent (20%) of the then
outstanding  Registrable  Securities  must  first  give the  Company a Notice of
Resale indicating such Stockholder's or Stockholders' intention to sell at least
five percent (5%) of the then outstanding Registrable Securities pursuant to the
Shelf Registration (or Subsequent Registration, as applicable).

                           (iii) Upon receipt of such Notice of Resale (unless a
certificate  of the President or the Chief  Financial  Officer of the Company is
delivered as provided in Section 4.3.2(b) below),  the Company will give written
notice to all  Stockholders  as soon as  practicable,  but in no event more than
seven (7)  business  days after the  Company's  receipt of such Notice of Resale
that either: (A) the prospectus contained in the registration  statement for the
Shelf  Registration (or Subsequent  Registration,  if applicable) is current (it
being  acknowledged  that it may be necessary for the Company during this period
to supplement the prospectus or make an appropriate filing under the 1934 Act so
as to cause the prospectus to become  current) and that (as  applicable) (1) the
Permitted  Window will commence on the date of such notice by the Company or (2)
the Company is required  under the 1933 Act and the  regulations  thereunder  to
amend the  registration  statement  for the Shelf  Registration  (or  Subsequent
Registration,  as applicable) in order to cause the prospectus to be current. In
the event that the Company  determines  that an  amendment  to the  registration
statement is necessary as provided  above, it will file and cause such amendment
to  become  effective  as soon as  practicable;  whereupon  it will  notify  the
Stockholders that the Permitted Window will then commence.
                           
                           (iv) There  will be no more than three (3)  Permitted
Windows  during  the  Registration  Period  and there  will be at least a 30-day
interval between any two (2) Permitted  Windows.  Company shall not be obligated
to keep the registration statement for the Shelf Registration (or any Subsequent
Registration)  current  during any period  other than a  Permitted  Window.  If,
pursuant to Section  4.3.2(b),  the Company defers a Permitted  Window,  and the
Stockholders  withdraw their Notice of Resale,  then such  withdrawal  shall not
count as a Permitted  Window.  The  Stockholders may elect to withdraw a request
for  registration  pursuant to a Notice of Resale and such withdrawal  shall not
count as a Permitted Window; provided however, that if the Company has commenced
preparation of any supplement or amendment to the registration  statement or any
part  thereof in response to such Notice of Resale  prior to  receiving  written
notice  from  the   Stockholders'   of  the  withdrawal  of  their  request  for
registration,  then the Stockholders who originally gave the Company such Notice
of Resale will  promptly  reimburse  Company for its actual  costs and  expenses
reasonably incurred in preparing and/or filing such supplement and/or amendment.

                  (h) Trading Window  Compliance.  The Stockholders  acknowledge
that the Company maintains an Insider Trading  Compliance Program and an Insider
Trading Policy,  as such may be amended (the "Company  Trading Policy") and that
the Company Trading Policy requires that those  directors,  officers,  employees
and other  persons  whom the  Company  determines  to be "Access  Personnel"  or
otherwise subject to the "trading window" and pre-clearance  requirements of the
Company Trading Policy (and members of their immediate  families and households)
are  permitted  to effect  trades in Company  securities:  (i) only during those
specified time periods  ("trading  windows") in which such persons are permitted
to make sales,  purchases or other trades in the Company's  securities under the
"trading window"  provisions of the Company Trading Policy;  and (ii) only after
pre-clearance  of such  sales,  purchases  or other  trades  with the  Company's
Insider Trading  Compliance  Officer.  If a Stockholder is or becomes subject to
the "trading  window" and/or  "pre-clearance"  provisions of the Company Trading
Policy described above, then,  notwithstanding  anything herein to the contrary,
such Stockholder may sell,  transfer and dispose of Registrable  Securities only
during those  trading  windows  during which such Company  Access  Personnel are
permitted to effect trades in Company stock under the Company Trading Policy and
only  after   pre-clearing  such  trades  with  the  Company's  Insider  Trading
Compliance Officer as provided in the Company Trading Policy. Semaphore is not a
stockholder to which the Company Trading Policy applies.

                  4.3.2 Registration.  Notwithstanding the provisions of Section
4.3.1 above, the Company shall not be obligated to effect any such registration,
qualification  or compliance  pursuant to this Section 4.3, and the  Stockholder
shall not be entitled to sell the Shares pursuant to any registration  statement
filed under Section 4.3 of this Agreement, as applicable:

                  (a)     if Form S-3 is not then available for such offering 
by the Stockholder;

                  (b)  if  the  Company  shall  furnish  to  the  Stockholder  a
certificate  signed by the President or Chief  Executive  Officer of the Company
stating  that in the  good  faith  judgment  of the  Board of  Directors  of the
Company,  it would be seriously  detrimental to the Company and its stockholders
for such  Permitted  Window  to be in effect at such  time,  in which  event the
Company  shall  have the right to defer a  Permitted  Window for a period of not
more  than  sixty  (60)  days  after  receipt  of a Notice  of  Resale  from the
Stockholder or Stockholders  pursuant to Section  4.3.1(f);  provided,  however,
that the Company may so  postpone a Permitted  Window no more than twice  during
the Registration Period; and provided further,  that if the Company so postpones
a Permitted Window, then  notwithstanding the last sentence of Section 4.3.1(a),
the Registration  Period of the Shelf Registration shall be extended by a period
of time equal to the period of  postponement  plus, if a Permitted  Window is in
effect at the end of such extended  Registration Period, the Registration Period
of the Shelf Registration shall be further extended until the expiration of such
thirty day Permitted  Window  (subject to the  provisions of Section 3 above and
Section 4.3.3 below);  and provided further,  that if Company defers a Permitted
Window as provided herein and the Stockholders  withdraw their Notice of Resale,
then such withdrawal shall not count as a Permitted Window;

                  (c)     if the Company is acquired and its Common Stock 
ceases to be publicly traded;

                  (d) in any particular  jurisdiction in which the Company would
be required to qualify to do business or to execute a general consent to service
of process in effecting such registration, qualification or compliance.

                  (e) if the SEC refuses to declare such registration  effective
due to the  participation  of any particular  Stockholder  in such  registration
(unless such Stockholder withdraws all such Stockholder's Registrable Securities
from such registration statement).

                  4.3.3 Shares  Otherwise  Eligible for Resale.  Notwithstanding
anything herein to the contrary, the Company shall not be obligated to effect or
continue  to keep  effective  any  such  registration,  registration  statement,
qualification  or compliance with respect to the Registrable  Securities held by
any particular Stockholder:

                  (a) if the Company or its legal  counsel shall have received a
"no-action"  letter or similar  written  confirmation  from the SEC that all the
Registrable  Securities  then  held by such  Stockholder  may be  resold by such
Stockholder within a three (3) month period without  registration under the 1933
Act pursuant to the  provisions of Rule 144  promulgated  under the 1933 Act (or
successor provisions), or otherwise;

                  (b) if legal  counsel to the Company  shall  deliver a written
opinion to the Company,  its transfer  agent and the  Stockholders,  in form and
substance  reasonably  acceptable  to the  Company and the  Stockholder,  to the
effect that all the Registrable  Securities then held by such Stockholder may be
resold by such Stockholder within a three (3) month period without  registration
under the 1933 Act pursuant to the provisions of Rule 144 promulgated  under the
1933 Act, or otherwise; or

                  (c)  after  expiration  or  termination  of  the  Registration
Period.

                  4.3.4 Expenses. The Company shall pay all expenses incurred in
connection  with each  registration  requested  pursuant  to this  Section  4.3,
(excluding  underwriters'  or brokers'  discounts  and  commissions),  including
without  limitation all filing,  registration and  qualification,  printers' and
accounting  fees and the reasonable  fees and  disbursements  of counsel for the
Company and one counsel for the Stockholders.

         4.4  Furnish  Information.  It shall be a  condition  precedent  to the
obligations  of the Company to take any action  pursuant to this  Agreement that
the selling Stockholders will furnish to the Company such information  regarding
themselves,  the Registrable Securities held by them, and the intended method of
disposition and plan of distribution of such Registrable  Securities as shall be
required to timely effect the registration of their Registrable Securities.

         5. Injunctive and Other Relief.  The Company and the Stockholder  agree
that in the event that either party breaches this Agreement,  the  non-breaching
party will be irreparably  harmed and will be entitled to injunctive  relief and
specific enforcement in addition to any other remedy which it may have at law or
in equity.  No  Stockholder  will have any right to obtain or seek an injunction
restraining or otherwise  delaying any registration  that is the subject of this
Agreement as the result of any controversy  that might arise with respect to the
interpretation or implementation of this Agreement.

         6. Entire Agreement; Modification. This Agreement sets forth the entire
agreement  and  understanding  between  the parties  hereto with  respect to the
subject matter hereof,  and merges and supersedes any and all prior discussions,
agreements,  and understandings  between or among them with respect thereto, and
no  party   shall  be  bound  by  any   condition,   definition,   warranty   or
representation,  other than those  expressly  set forth or provided  for in this
Agreement or in any document or instrument delivered pursuant to this Agreement,
or as may be set forth in writing and signed by the party or parties to be bound
thereby on or subsequent to the date hereof.  This  Agreement may not be changed
or modified,  except by an agreement in writing  executed by the Company and the
Stockholder.

         7. Governing  Law. This  Agreement  shall be governed by California law
(excluding the choice of law provisions) and applicable Federal law.

         8.  Severability.  If any  term,  provision,  covenant  or  restriction
contained in this Agreement is held by a court of competent  jurisdiction  to be
invalid,  void, or  unenforceable,  then the remainder of this  Agreement  shall
remain  operative and in full force and effect.  If any  provision  contained in
this Agreement is invalidated or becomes inoperative because of a change in law,
the  parties  hereto  will use  their  best  efforts  to  adopt  an  appropriate
substitute  (if any) for  such  provision  consistent  with  the  intent  of the
parties.

         9. Binding Effect of Agreement.  The terms of this  Agreement  shall be
binding on and inure to the benefit of the parties  hereto and their  respective
subsidiaries,  parents or other affiliated entities,  agents, attorneys,  heirs,
executors, successors, representatives and assigns.

         10. Notices.  All notices,  requests,  demands and other communications
hereunder  shall be in  writing  and shall be deemed to have been duly  given if
delivered  by (i) hand,  (ii)  certified  or  registered  mail,  return  receipt
requested,  (iii) facsimile (with confirmation  receipt) or (iv) prepaid courier
service,  to the  following  addresses:  (a) if to the  Company to 217  Humboldt
Court, Sunnyvale, CA 94089, Attention: Chief Financial Officer and (b) if to the
Stockholder, to Semaphore Communications Corporation,  800 Long Ridge Road, P.O.
Box 1600, Stamford,  Connecticut 06904, Attention: Chief Financial Officer, with
a copy to Semaphore  Communications  Corporation,  800 Long Ridge Road, P.O. Box
1600, Stamford, Connecticut,  Attention: General Counsel or to such other person
or persons or to such other  address or addresses as may be designated by one to
the other.

         11. Counterparts.  This Agreement may be executed in counterparts, each
of which will be deemed an original,  but all of which together will  constitute
one and the same instrument.

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

DIGITAL LINK CORPORATlON


By: /s/ Stanley E. Kazmierczak, CFO



SEMAPHORE COMMUNICATIONS CORPORATION


By: /s/ Timothy da Silva, President & CEO