EXHIBIT 10.9

                  SIXTH AMENDMENT TO LEASE AGREEMENT PRIVATE


     This Sixth Amendment to Lease Agreement  ("Agreement")  is made and entered
into as of this  1st day of  October,  1997,  by and  between  The  Mutual  Life
Insurance Company of New York with offices at 1740 Broadway,  New York, New York
10019 (the "Landlord"), and Dialogic Corporation, a New Jersey corporation, with
offices and a principal place of business located at 1515 Route 10,  Parsippany,
New Jersey 07054 (the "Tenant").

                               W I T N E S S E T H

     WHEREAS,   Landlord  is  the  owner  of  the  real  property  and  all  the
improvements  thereon  located at 1515  Route 10,  Parsippany,  New Jersey  (the
"Building"); and,

     WHEREAS,  Tenant  desired to lease from  Landlord and  Landlord  desired to
lease to Tenant  approximately  115,000 square feet of office space on the first
and second floors of the Building and 10,000 square feet of storage space on the
basement level (the "Original Premises"); and,

     WHEREAS,  on or about  September 1, 1993 Landlord and Tenant entered into a
written Lease Agreement (the "Original Lease") for the Premises; and,
 
     WHEREAS,  during January 1994 a first  amendment to the Original Lease (the
"First Amendment") was proposed, but never agreed upon or effective; and,

     WHEREAS,  as of January 20, 1994 Landlord and Tenant  entered into a Second
Amendment to Lease Agreement (the "Second Amendment"); and,

     WHEREAS, as of July 19, 1994 (notwithstanding that the Fourth Amendment, as
defined below,  references the date of the Third Amendment as of March 10, 1994)
Landlord and Tenant  entered  into a Third  Amendment  to Lease  Agreement  (the
"Third Amendment"); and,

     WHEREAS,  as of December 20, 1994 Landlord and Tenant entered into a Fourth
Amendment to Lease Agreement (the "Fourth Amendment"); and,

     WHEREAS,  as of April 15, 1996,  Landlord  and Tenant  entered into a Fifth
Amendment to Lease Agreement (the "Fifth Amendment", the Second Amendment, Third
Amendment,  Fourth Amendment and Fifth Amendment are collectively referred to as
the  "Amendments";  and the Original Lease,  as modified by the  Amendments,  is
referred to as the "Lease"); and,

     WHEREAS,  Landlord  and  Tenant do now  hereby  desire to amend and  modify
certain terms of the Lease as more particularly set forth below.

     NOW,  THEREFORE,  it is hereby agreed that in  consideration  of the mutual
covenants contained herein, and for such other good and valuable  consideration,
the sufficiency of which are hereby mutually acknowledged by the parties hereto,
Landlord and Tenant agree as follows:

     1. Capitalized terms used but not otherwise defined herein shall have their
meanings described to them in the Lease.  Furthermore,  in addition to the terms
elsewhere defined herein, the following terms shall have the following meanings:
(a) "Seventh Expansion Space" shall mean approximately 19,630 square feet on the
third  floor of the  Building,  as shown on the  floor  plan  annexed  hereto as
Exhibit A and made a part  hereof.  (b)  "Eighth  Expansion  Space"  shall  mean
approximately 8,053 square feet on the first floor of the Building,  as shown on
the floor plan annexed hereto as Exhibit B and made a part hereof. (c) "Basement
Expansion Space" shall mean  approximately  8,000 square feet of the basement of
the Building as shown on the floor plan  annexed  hereto as Exhibit C and made a
part hereof.  (d) "Seventh Rental  Commencement  Date" shall mean the earlier of
(i) the date upon which  Landlord's  Work (as defined below) in connection  with
the Seventh Expansion Space has been substantially  completed,  or (ii) the date
Tenant  shall  occupy any of the Seventh  Expansion  Space.  (e) "Eighth  Rental
Commencement  Date" shall mean the earlier of (i) the date upon which Landlord's
Work in  connection  with the  Eighth  Expansion  Space  has been  substantially
completed,  or (ii) the date  Tenant  shall  occupy any of the Eighth  Expansion
Space.

     2. Tenant warrants,  covenants and acknowledges that as of the date hereof,
to the best of its knowledge:  a) Landlord is not in default under the Lease and
no event has occurred which, with the giving of notice or the passage of time or
both,  would  constitute a default under the Lease as modified by this Agreement
on the  part of the  Landlord;  b)  Tenant  does not  contest  the  validity  or
enforceability  of the Lease and this  Agreement,  and  Tenant  has no claims or
defenses  as to  obligations  under  the  Lease  and this  Agreement  and is not
entitled to any offset or abatement with respect thereto,  except for Landlord's
obligation under Section 12 of this Agreement;  c) Landlord has performed all of
its  obligations of an executory  nature  (including all  construction  required
under the Lease)  pursuant to the terms and  provisions of the Lease  (including
Landlord's  obligations  with  respect  to the  Fourth  Expansion  Space,  Fifth
Expansion Space and Sixth Expansion Space [as such terms are defined below]); d)
the  Commencement D ate, as such term is defined in the Lease was June 13, 1994,
and the Expiration  Date, as defined in the Lease (without  giving effect to any
renewal  options,  but  giving  effect  to  paragraphs  10 and 22 of the  Fourth
Amendment)  is June 14,  2005;  e) the Lease is in full force and effect and has
not been  amended  or  modified  except by this  Agreement;  f) Tenant is not in
default in the  performance of the Lease and has not committed any breach of the
Lease and  Tenant  is not the  subject  of any  federal  or  state,  bankruptcy,
insolvency or liquidation  proceeding;  and g) Except for the Seventh  Expansion
Space,  and the  Eighth  Expansion  Space,  Tenant has  accepted  and is in full
possession  of the  Premises (as defined  below),  including  all  improvements,
additions,  and  alterations  thereto  required to be made by Landlord under the
Lease.

     3. (a) In addition to those premises that Landlord has previously leased to
Tenant and Tenant has previously  leased from Landlord  pursuant to the Original
Lease and the  Amendments,  Landlord  hereby  leases to Tenant and Tenant hereby
leases  from  Landlord  the  following  additional  premises:  (i)  the  Seventh
Expansion  Space,  (ii) the  Eighth  Expansion  Space,  and (iii)  the  Basement
Expansion  Space.  Within  thirty  (30) days of the  signing of this  Agreement,
Landlord shall cause the Seventh Expansion Space, the Eighth Expansion Space and
the Basement  Expansion Space to be measured pursuant to the BOMA method and the
exact square footage shall be deemed fixed. Promptly thereafter,  landlord shall
deliver tenant the measured dimensions.

     (b) It is the intent of the  parties  hereto that the  "Premises",  as such
term is defined in the Original Lease and which has been redefined and increased
pursuant to certain of the Amendments,  shall be further redefined and increased
and shall now  incorporate the Seventh  Expansion  Space,  the Eighth  Expansion
Space and the Basement  Expansion  Space as well as all of the space  previously
demised to the Tenant, including the following: the Original Premises, the First
Expansion  Space (as such term is  defined in the Third  Amendment),  the Second
Expansion  Space and Third  Expansion  Space (as such  terms are  defined in the
Fourth  Amendment),  the Fourth Expansion Space, Fifth Expansion Space and Sixth
Expansion  Space  (as such  terms  are  defined  in the  Fifth  Amendment).  All
references to the Premises in the Lease as modified  herein,  shall refer to the
Premises  as defined in this  Agreement,  unless the  context  clearly  requires
otherwise.

     4 (a) In addition  to the Fixed Rent  previously  reserved by the  Original
Lease and certain of the Amendments,  Tenant shall pay to Landlord,  without any
prior notice or demand therefore and without any abatement,  deduction or setoff
whatsoever,  in lawful  money of the  United  States of  America,  by check,  at
Landlord's office or such other place Landlord may designate,  additional annual
base rent,  (such  additional  annual base rent shall be  incorporated  into the
defined term "Fixed Rent") payable in equal monthly  installments  in advance on
the first day of each and every month during the term of this lease as follows:

         (i) Fixed Rent for the Seventh Expansion Space ("Seventh Expansion 
     Space Rent") shall be payable:

               (1)  from  the  Seventh  Rental  Commencement  Date  through  and
          including May 31, 1999, at the annual rate of $304,265.00,  payable in
          equal monthly installments each in the amount of $25,355.42;

               (2) from June 1, 1999, through and including May 31, 2004, at the
          annual rate of $343,525.00, payable in equal monthly installments each
          in the amount of $28,627.08; and

               (3) from June 1, 2004,  through and  including  June 14, 2005, at
          the annual rate of $395,151.90,  payable in equal monthly installments
          each in the amount $32,929.33;

          (ii) Fixed Rent for the Basement Expansion Space ("Basement  Expansion
     Space Rent") shall be payable  from the date hereof  through and  including
     June 14, 2005, at the annual rate of  $32,000.00,  payable in equal monthly
     installments each in the amount $2,666.67;

          (iii) Fixed Rent for the Eighth  Expansion  Space  ("Eighth  Expansion
     Space Rent") shall be payable:

               (1)  from  the  Eighth  Rental   Commencement  Date  through  and
          including May 31, 1999, at the annual rate of $136,901.00,  payable in
          equal monthly installments each in the amount of $11,408.42;

               (2) from June 1, 1999, through and including May 31, 2004, at the
          annual rate of $140,927.50, payable in equal monthly installments each
          in the amount of  $11,743.96;  and (3) from June 1, 2004,  through and
          including June 14, 2005, at the annual rate of $162,106.89, payable in
          equal monthly installments each in the amount $13,508.91.

          (b)  Tenant  shall  be  obligated  to  pay  its  electrical  costs  in
accordance with the terms of the Lease, as amended herein.

          (c)  Notwithstanding  anything else contained in this  Agreement,  the
parties acknowledge that the Seventh Expansion Space and Eighth Expansion Space,
might not be  substantially  completed  simultaneously.  Should such  completion
dates not be  simultaneous,  the  obligation of the Tenant to pay Fixed Rent and
Additional Rent, respectively, in accordance with Section 4(a) above and Section
9 below for the space that is  substantially  completed  is  independent  of its
obligations regarding the space not yet substantially completed. Tenant shall be
obligated to accept such substantially  completed premises and to pay Fixed Rent
and Additional Rent in accordance with this Agreement for the space that is then
substantially  completed.  (By way of example and not of limitation,  should the
Seventh Expansion Space be substantially completed prior to the Eighth Expansion
Space,  commencing on the Seventh Rental Commencement Date, Tenant shall pay the
Seventh  Expansion Space Rent, in addition to the Fixed Rent otherwise  required
pursuant  to  the  terms  of  the  Lease,  as  amended   herein,   and  Tenant's
Proportionate Share shall increase by 9%).

          (d) Intentionally Omitted.

          (e) If the Seventh Rental  Commencement  Date and/or the Eighth Rental
Commencement  Date is a date other than the first  date of the  calendar  month,
then the Seventh Expansion Space Rent and/or the Eighth Expansion Space Rent, as
the case may be, shall be prorated on a per diem basis for the calendar month in
which the respective commencement date occurs. A similar credit shall be granted
against  the Fixed Rent  installment  due during the month which is the month of
the Expiration Date.

          5. (a)  Within  ten (10)  days  from the  date  Tenant  executes  this
Agreement,  Tenant shall (i) prepare and deliver to Landlord  line  drawings and
any  and  all  related  plans  and  specifications  (collectively  the  "Seventh
Expansion Plans and  Specifications")  for the Seventh Expansion Space, and (ii)
prepare and deliver to Landlord  line drawings and any and all related plans and
specifications,  including  Tenant's  selection  of paint color and carpet color
(collectively  the "Eighth Expansion Plans and  Specifications")  for the Eighth
Expansion   Space,   provided,   however,   the  Eighth   Expansion   Plans  and
Specifications shall not include any demolition plans. Landlord will prepare and
deliver  to  Tenant  construction  drawings  ("Construction  Drawings")  for the
Seventh  Expansion Space and Eighth  Expansion Space consistent with the Seventh
Expansion  Plans  and   Specifications   and  the  Eighth  Expansion  Plans  and
Specifications   (the  cost  of  such   Construction   Drawings   shall  be  the
responsibility of the parties as stated in Section 5(c) below).  Within five (5)
business  days (the fifth  business  day shall be  referred  to as the  "Outside
Construction  Drawing  Approval Date") of receipt of the  Construction  Drawings
from  Landlord,  Tenant  will  deliver to  Landlord  written  notice that it has
approved or disapproved  the  Construction  Drawings,  provided,  however,  that
Tenant's  disapproval  must be in  Tenant's  reasonable  discretion,  and, if it
disapproves of the Construction Drawings, Tenant shall specify in writing and in
reasonable  detail,  any objections to the Construction  Drawings.  In the event
that Tenant disapproves of the Construction Drawings,  Landlord and Tenant shall
promptly  meet and use good faith  efforts to resolve  such  disagreement.  That
period of time from the day following the Outside  Construction Drawing Approval
Date through the date that the Tenant approves the  Construction  Drawings,  but
only to the  extent  that  such  period is not the  result  of the  Construction
Drawings being  materially  inconsistent  with the Seventh  Expansion Plans an d
Specifications  and the  Eighth  Expansion  Plans and  Specifications,  shall be
referred to as "Approval Delay". Landlord shall not proceed with Landlord's Work
(as  defined  below)  until  Tenant  has  provided   written   approval  of  the
Construction Drawings.

          (b) Landlord shall perform the following work ("Landlord's Work"): (i)
prepare  the Seventh  Expansion  Space  (including  the  demolition  thereof) in
accordance  with  the  Seventh  Expansion  Plans  and   Specifications  and  the
Construction Drawings, and (ii) prepare the Eighth Expansion Space in accordance
with  the  Eighth  Expansion  Plans  and  Specifications  and  the  Construction
Drawings.  Except as provided in this  Subsection  (b),  Landlord  shall have no
obligation  to perform  any work with  respect to the  balance of the  Premises,
including, but not limited to, the Basement Expansion Space.

          (c) Landlord  shall,  in connection  with  Landlord's  Work, be solely
responsible  for the  following:  (i) up to but no more than  $39,260.00  of the
costs and  expenses  ("Design  Allowance")  associated  with  architectural  and
engineering  design  and plans and  Construction  Drawings  with  respect to the
Seventh  Expansion  Space;  (ii) up to but no more than $392,600.00 of the costs
and expenses ("Seventh  Construction  Allowance")  associated with substantially
completing the Seventh  Expansion Space in accordance with the Seventh Expansion
Plans and Specifications and the Construction Drawings (provided,  however, that
none of the Seventh Construction  Allowance shall be allocated for demolition of
the  Seventh  Expansion  Space);  (iii)  all  costs  and  expenses  in excess of
$21,593.00  with  respect to the  demolition  of the  Seventh  Expansion  Space,
provided,  however Landlord's liability shall not exceed $25,000; and (iv) up to
but no more than  $40,265.00  of the costs and  expenses  ("Eighth  Construction
Allowance") associated with subs tantially completing the Eighth Expansion Space
in  accordance  with the  Eighth  Expansion  Plans  and  Specifications  and the
Construction Drawings,  (the amounts which Landlord has agreed to incur in order
to perform Landlord's Work shall be referred to as "Landlord's Allowance").  The
Design  Allowance,   Seventh  Construction  Allowance  and  Eighth  Construction
Allowance  may  not  be  used  for  any  purpose  other  than  for  the  purpose
specifically  provided  for  herein,  and to the extent  the costs and  expenses
associated  with the work to be done  thereunder  are less  than the  respective
allowance, the excess of each, if any, shall accrue for the benefit of Landlord,
and Tenant shall have no claim to same.  Tenant shall be solely  responsible for
all costs and expenses which exceed Landlord's Allowance; it being the intent of
the parties that Tenant pay said excess as Additional Rent and such sum(s) shall
be payable by Tenant  within  thirty (30) days after  receipt of an invoice from
Landlord, provided, however, such payment date shall in no event be earlier than
thirty(30)  days  from the  substantial  completion  of the  space for which the
particular payment applies. Except as provided in this Subsection (c) and except
in accordance  with Section 12, Landlord shall have no obligation to pay for any
work with respect to the Premises,  including,  but not limited to, any work for
the  Basement  Expansion  Space  and any  costs  and  expenses  associated  with
architectural  and engineering  design and plans and Construction  Drawings with
respect to the Eighth Expansion Space.

          (d) Landlord shall use reasonable efforts,  including the solicitation
of at  least  three  (3)  competitive  bids  where  appropriate  from  reputable
contractors to obtain the  construction of Landlord's Work at a reasonable cost.
Landlord agrees to solicit bids from March Associates,  DDB Interior Contracting
and Turner  Construction  Company.  Landlord  shall  promptly  deliver to Tenant
copies of all bids that Landlord receives with respect to the foregoing.  Tenant
shall, within seven (7) business days of receipt of said information, select the
winning  bidder  ("Winning  Bidder")  from the bids  delivered  to Landlord  and
Landlord  shall award the contract to such bidder.  If the Winning Bidder is not
March  Associates,  Tenant shall pay to Landlord,  as Additional Rent, on demand
upon substantial completion of Landlord's Work, an oversight and plan review fee
of three (3%) percent of the contract  price entered into with Winning Bidder in
effecting Landlord's Work.

          (e) If Tenant  requests  to amend,  modify or change the  Construction
Drawings,  after such  Construction  Drawings have been approved by Landlord and
Tenant ("Change Order"), Tenant shall submit to Landlord for its approval (which
shall not be  unreasonably  withheld) a reasonably  detailed  description of the
proposed Change Order in writing.  Within seven (7) business days after receipt,
Landlord  shall  notify  Tenant  whether it approves or  disapproves  the Change
Order.  If Landlord  approves  the Change  Order,  Landlord  shall  evidence its
approval of such Change  Order by  executing  the Change  Order or a  memorandum
thereof.  Failure by Landlord to notify Tenant within seven (7) business days of
its  approval or  disapproval  of the Change  Order shall be deemed to mean that
Landlord has disapproved  the Change Order.  Landlord may require changes to the
Construction  Drawings if necessary as a result of any Change Order or to comply
with changes, revisions or additions to applicable building codes and other laws
(collectively,  ("Landlord  Change Orders").  Within five(5) business days after
receipt, Tenant shall notify Landlord in writing of its approval (which approval
will not be unreasonably withheld) or disapproval of all Landlord Change Orders;
Landlord  shall not proceed with such Landlord  Change Orders  without  Tenant's
approval.  If Tenant shall so notify Landlord of its disapproval of any Landlord
Change  Order,  such written  notice shall include  reasonable  detail as to the
reason for such  disapproval.  Landlord  shall,  within seven (7) business  days
after  receipt  thereof,  make  the  necessary  revisions  requested  by  Tenant
(provided,  however,  that such  revisions are in full  compliance  with law and
otherwise reasonably  acceptable to Landlord) and resubmit the same for Tenant's
approval ("Revised Landlord Change Order"). Upon receipt of the Revised Landlord
Change Order,  Tenant shall within three (3) business days,  notify  Landlord in
writing of its approval or disapproval of the Revised  Landlord Change Order. In
the event Tenant disapproves of the Revised Landlord Change Order,  Landlord and
Tenant  shall   promptly  meet  and  use  good  faith  efforts  to  resolve  any
disagreement.  The period of time from the day following Tenant's disapproval of
the Revised  Landlord Change Order through the day that Tenant shall approve the
Landlord Change Order shall be deemed an Approval Delay.

          (f) Subject to  Unavoidable  Delays (as defined in Section 38.2 of the
Original  Lease)  and  Tenant  Delays,  (as  defined  herein),   Landlord  shall
substantially  complete  Landlord's  Work (i) in  connection  with  the  Seventh
Expansion  Space,  on or before May 1,  1998,  and (ii) in  connection  with the
Eighth Expansion Space, on or before May 1, 1998,  provided,  however,  that the
Lease,  as modified  herein,  and the  obligations  of the  Landlord  and Tenant
hereunder shall nevertheless continue in full force and effect.  Notwithstanding
the foregoing,  if the Eighth  Expansion Plans and  Specifications  provide that
only painting and  carpeting of the Eighth  expansion  Space be performed  then,
subject to Unavoidable  Delays and Tenant Delays  Landlord  shall  substantially
complete painting and carpeting the Eighth Expansion Space on or before March 1,
1998.  Except as provided below,  Landlord shall have no liability to Tenant for
any delay in delivering the Seventh  Expansion Space and/or the Eighth Expansion
Space.  Notwithstanding the f oregoing, (x) if delivery of the Seventh Expansion
Space is delayed by the acts or omissions of Landlord  beyond June 1, 1998, (or,
if the Winning  Bidder is March  Associates,  May 1, 1998) as such date has each
been  extended by the number of days  attributable  to a Tenant  Delay and/or an
Unavoidable  Delay ("Seventh  Outside Date"),  then the Tenant shall receive one
day of free  Seventh  Expansion  Space Rent for each two days  during the period
from the  Seventh  Outside  Date to the  substantial  completion  of the Seventh
Expansion Space, and (y) if delivery of the Eighth Expansion Space is delayed by
the acts or  omissions  of  Landlord  beyond  June 1, 1998,  (or, if the Winning
Bidder is March Associates,  May 1, 1998) as such date has each been extended by
the number of days  attributable  to a Tenant Delay and/or an Unavoidable  Delay
("Eighth  Outside  Date"),  then the Tenant shall receive one day of free Eighth
Expansion Space Rent for each two days during the period from the Eighth Outside
Date to the substantial completion of the Eighth Expansion Space.

          (g)  Landlord's   Work  shall  be  deemed   substantially   completed,
notwithstanding  the  fact  that  minor  details  of  construction,   mechanical
adjustments  or  decoration  remain  to be  performed  that  do  not  materially
interfere  with  Tenant's use of the Seventh  Expansion  Space and/or the Eighth
Expansion  Space,  as  the  case  may  be,  or  its  business,  provided  that a
Certificate  of Occupancy  (whether  permanent or temporary) has been issued (if
required).  Notwithstanding  the  foregoing,  to the  extent  that  the  Seventh
Expansion  Space is not ready for  occupancy by Tenant on May 1, 1998 and/or the
Eighth  Expansion  Space is not ready for occupancy by Tenant on May 1, 1998 (or
on March 1, 1998, if the Eighth Expansion Plans and Specifications  provide that
only painting and carpeting of the Eighth expansion Space be performed),  solely
due to one or more Tenant Delays (as defined below),  then the Seventh Expansion
Space  and/or  the Eighth  Expansion  Space (as the case may be) shall be deemed
substantially  completed on the date when s aid space would  otherwise have been
substantially completed but for such Tenant Delay. Landlord shall be responsible
for obtaining the initial permanent Certificate of Occupancy,  if required, even
if  Tenant  assumes  occupancy  under  a  temporary  Certificate  of  Occupancy;
provided,  however, if a permanent  Certificate of Occupancy is conditioned upon
the  performance of additional  work to the Seventh  Expansion  Space and/or the
Eighth  Expansion  Space,  as the case may be, said work shall be  performed  by
Tenant at its sole cost and expense (to the extent Landlord's Allowance has been
exceeded, and if Landlord's Allowance has not been exceeded, if said work is not
within the scope of  Landlord's  Work),  subject  to  Section 7 of the  Original
Lease, as amended.

          (h) The term  "Tenant  Delay"  shall  mean any delay in  substantially
completing  Landlord's  Work  and/or  any  delay  in the date  that the  Seventh
Expansion  Space  and/or the  Eighth  Expansion  Space  shall be  available  for
Tenant's  occupancy,  which is solely due to any act or omission of Tenant,  its
agents,  employees,  contractors  or anyone  acting under or for Tenant.  Tenant
Delay shall also  include the  following,  (but only to the extent that any such
delays  are  the  cause  of  Landlord's  inability  to  substantially   complete
Landlord's  Work  and/or  are the  cause of the any  delay in the date  that the
Seventh Expansion Space and/or the Eighth Expansion Space shall be available for
Tenant's  occupancy):  (i) delays by Tenant in delivering the Seventh  Expansion
Plans and Specifications  and/or the Eighth Expansion Plans and  Specifications;
(ii) delays arising solely from changes by Tenant to the Seventh Expansion Plans
and Specifications  and/or the Eighth Expansion Plans and Specifications;  (iii)
delays resulting from Tenant's direction to Landlord to suspend Landlord's Work;
(iv) delays by Tenant in delivering  approval or disapproval to the Construction
Drawings;  (v) any  Approval  Delay;  (vi) delays  arising as result of a Change
Order  requested by Tenant;  (vii)  delays by Tenant in  approving  any Landlord
Change Orders; and (viii) delays by Tenant in selecting the Winning Bidder.

          (i) Notwithstanding  anything to the contrary contained herein, if (i)
the Seventh Rental  Commencement  Date does not occur on or before  September 1,
1998,  as such date is extended by the number of days  attributable  to a Tenant
Delay  and/or  Unavoidable  Delay,  (such  date,  as  extended is referred to as
"Seventh  Tenant  Outside  Date") then the Tenant may, as its sole and exclusive
remedy,  terminate  the  portion  of  this  Agreement  relating  to the  Seventh
Expansion  Space by giving written  notice to Landlord no later than  twenty-one
(21)  days  from  such  Seventh  Tenant  Outside  Date and the  portion  of this
Agreement  relating only to the Seventh  Expansion  Space shall terminate on the
date which is fifteen (15) days after Landlord's receipt of such notice,  unless
prior to such date the Seventh Rental  Commencement  Date occurs,  in which case
Tenant's  termination  notice  shall be null and void and this  Agreement  shall
continue in full force and effect;  and/or (ii) the Eighth  Rental  Commencement
Date does not occur on or befor e September 1, 1998, as such date is extended by
the number of days  attributable  to a Tenant  Delay and/or  Unavoidable  Delay,
(such date, as extended is referred to as "Eighth Tenant Outside Date") then the
Tenant  may, as its sole and  exclusive  remedy,  terminate  the portion of this
Agreement  relating to the Eighth  Expansion  Space by giving  written notice to
Landlord no later than twenty-one (21) days from such Eighth Tenant Outside Date
and the portion of this Agreement  relating only to the Eighth  Expansion  Space
shall terminate on the date which is fifteen (15) days after Landlord's  receipt
of such notice,  unless prior to such date the Eighth Rental  Commencement  Date
occurs,  in which case  Tenant's  termination  notice shall be null and void and
this Agreement shall continue in full force and effect. If Landlord is unable to
deliver the Seventh  Expansion Space and/or the Eighth  Expansion  Space, as the
case  may be,  in  accordance  with  the  terms of this  Agreement,  and  Tenant
terminates  the portion of this  Agreeme nt  relating  to the Seventh  Expansion
Space and/or the Eighth  Expansion  Space,  in accordance with the terms of this
Section,   then,  Landlord  shall  reimburse  Tenant  for  Tenant's  actual  and
reasonable  costs and expenses  incurred with respect to the demolition,  design
and  construction  of the  space  so  terminated.  6.  Notwithstanding  anything
contained  in the Lease,  including  Section 6.1 of the  Original  Lease as such
section  may have been  modified,  Tenant  agrees  that  Landlord  shall have no
obligation  to provide any  additional  funds with respect to  Landlord's  Work,
except as specifically provided in Section 5(c) above and in Section 12 below.

          7.  Landlord  will, at its own cost and expense  separately  meter the
Seventh  Expansion Space and Eighth  Expansion Space for electric usage.  Tenant
will, at its own cost and expense,  continue to have all electrical uses for the
Basement  Expansion  Space and the  portion of the  basement  demised  under the
Original Lease (the "Original  Basement Space")  connected to Tenant's  separate
electrical meter.

          8.  Notwithstanding  anything else  contained in the Original Lease or
any of the Amendments,  or herein, should Tenant exercise its option(s) to renew
the term of the leased premises,  as provided for in Section 2.5 of the Original
Lease,  said renewal term(s) shall be operative for the entire Premises (as such
term is defined herein).

          9. Tenant's  obligation to pay Tenant's  Proportionate  Share (as such
share shall be increased giving effect to the transaction  contemplated  herein)
of Operating Expenses and Taxes, as such obligations are expressed in the Lease,
shall commence,  (a) with respect to the Seventh Expansion Space, on the Seventh
Rental Commencement Date, and (b) with respect to the Eighth Expansion Space, on
the Eighth Rental  Commencement  Date.  Tenant and Landlord  agree that Tenant's
Proportionate  Share with  respect  to the  Seventh  Expansion  Space is 9%, and
Tenant's  Proportionate  Share with respect to the Eighth Expansion Space is 4%.
Notwithstanding  anything  to the  contrary  contained  in the  Lease or in this
Agreement, after both the Seventh Rental Commencement Date and the Eighth Rental
Commencement  Date,  Tenant's  Proportionate  Share with respect to the Premises
shall  equal  100%.  All other  items of  Additional  Rent  shall be  payable in
accordance with the terms of the Lease as modified herein. The Base Tax Year and
the Base Oper  ating  Expense  Year,  as  defined  in the  Lease,  shall  remain
unchanged for the purpose of calculating any and all charges to Tenant.

          10. Tenant has inspected the Premises,  including, but not limited to,
the Seventh Expansion Space,  Eighth Expansion Space and the Basement  Expansion
Space  and  accepts  the  same  "As  Is" in its  present  condition  subject  to
Landlord's  Work.  Acceptance of  possession by Tenant of the Seventh  Expansion
Space and/or the Eighth  Expansion  Space shall be the conclusive  evidence that
Landlord's  obligation  to  construct  said  accepted  premises  has been  fully
performed in accordance  with the  requirements  of this  Agreement,  except for
normal  punch  list  items and  except if within  thirty  (30) days  after  such
acceptance  date Tenant shall give  written  notice to Landlord  specifying  the
respects in which the same was not in such condition.

          11. All  tenant  improvements  constructed  in the  Seventh  Expansion
Space,  Eighth  Expansion  Space and the Basement  Expansion  Space,  whether by
Landlord or by (or on behalf of) Tenant,  and whether at  Landlord's or Tenant's
expense,  shall be subject to Section 7.4 of the Original  Lease, as it may have
been amended.  Notwithstanding  the foregoing,  all of Landlord's Work and other
tenant improvements which are a part of this Agreement shall become the property
of the Landlord and shall remain upon and be surrendered  with the Premises upon
the Expiration Date and need not be removed.

          12.  Notwithstanding  anything  to  the  contrary  contained  in  this
Agreement,  Landlord has consented to the erection of a certain chain link fence
and to the installation of lighting in the Basement  Expansion Space which is of
the same nature and quality as such items were previously supplied to Tenant for
the Original Basement Space.  Tenant represents that all such work was performed
by Tenant in a good and  workmanlike  manner,  in  compliance  with all federal,
state, municipal and other statutes,  laws, ordinances,  regulations,  rules and
requirements  relating  to  the  Building,  in  accordance  with  all  standards
established  by  Landlord  and  otherwise  in  compliance  with  the  terms  and
conditions of the Lease, as modified  hereby.  Within thirty (30) days after (a)
submission  to  Landlord  of a complete  and final  release and lien waiver with
respect to the Building  executed by all parties  with legal  standing to file a
lien,  and (b)  submission to Landlord of all invoices for the work so performed
and other items  reasonably r equested,  Landlord shall reimburse Tenant for the
actual costs and expenses  Tenant has incurred in performing  the work described
in this Section 12 in an amount not to exceed $21,825.00.

          13.  Tenant shall use the Basement  Expansion  Space  exclusively  for
storage and otherwise in compliance  with the terms and conditions of the Lease,
as modified herein.

          14.  (a) The  address  set forth  for  Landlord  (including  the those
parties to receive copies of notices, consents,  approvals,  requests, and other
communications  delivered to Landlord) in Section 28.1 of the Original  Lease is
hereby modified and amended as follows:


          To Landlord:

                            MONY REAL ESTATE INVESTMENT MANAGEMENT
                            c/o The Mutual Life Insurance Company of New York
                            1740 Broadway
                            Ninth Floor
                            New York, New York 10019
                            Attn.:  Real Estate Asset Management

          with a copy to:
                            The Mutual Life Insurance Company of New York
                            1740 Broadway
                            New York, New York 10019
                            Attn:  Real Estate Counsel

          (b) The address set forth for Tenant in Section  28.1 of the  Original
Lease is hereby modified and amended as follows: To Tenant: Dialogic Corporation
1515 Route Ten Parsippany,  New Jersey  07054-4596 Attn: Real Estate  Facilities
Manager

          Copies to Tenant  shall be  delivered  as  specified  in the  Original
Lease.

          15. Tenant and Landlord,  each  respectively  warrants and  represents
that it has not dealt with any broker or real estate  agent in  connection  with
this Sixth Amendment to Lease Agreement or its negotiation, other than Edward S.
Gordon  of New  Jersey  and  Cushman &  Wakefield  of New  Jersey  (collectively
"Broker"),  and  Landlord  agrees  to pay  the  Broker  pursuant  to a  separate
agreement. Each party shall indemnify and hold the other harmless from any cost,
expense or liability  (including  costs of suit and reasonable  attorneys' fees)
for any  compensation,  commission  or fees claimed by any real estate broker or
agent  or other  intermediary,  other  than  Broker,  in  connection  with  this
Agreement or its negotiation by reason of any act of the indemnifying party.

          16.  Tenant  agrees,  confirms and  acknowledges  that (a) there is no
remaining  expansion space square footage that Tenant has the option to lease as
such right was  specifically  set forth in Section 2.6 of the Original Lease, as
such  section was modified by the Second  Amendment,  and (b) Landlord has fully
complied with the provisions of Section 2.7 (which provides for Tenant to have a
right of first  refusal) and Tenant agrees that it has no further right of first
refusal with respect to any space in the Building other than that right of first
refusal  (as said  right is more  accurately  described  in  Section  2.7 of the
Original Lease "Right of First Refusal") for space that is currently unleased in
the basement of the Building  ("Remaining Basement Space"),  provided,  however,
that with  respect  to the Right of First  Refusal  for the  Remaining  Basement
Space,  (i) the last two  sentences  of Section  2.7 of the  Original  Lease are
deleted in their entirety, (ii) Tenant, at its sole cost and expense shall cause
to have  all  electrical  uses  for any of the  Remaining  Basement  Space it so
leases,  connected to Tenant's separate electrical meter, (iii) Tenant agrees to
accept the Remaining  Basement  Space in its condition and state of repair as of
the date of the  commencement of the lease for the Remaining  Basement Space and
Tenant  agrees that Landlord  shall not be required to perform any work,  supply
any materials or incur any expense to prepare such space for Tenant's occupancy,
(iv) the term of the lease for the Remaining Basement Space shall be co-terminus
with the Lease,  as  modified  herein,  and (v) Tenant  shall use the  Remaining
Basement  Space  exclusively  for storage and otherwise in  compliance  with the
terms and  conditions  of the Lease,  as modified  herein.  Time shall be of the
essence  with respect to Tenant's  notice in response to the Refusal  Notice (as
defined in Section 21 below)  with  respect to the Right of First  Refusal,  and
Tenant's failure to give any such notice within the ten (10) business day period
shall be deemed a re jection  of  Landlord's  offer,  any  principles  of law or
equity to the contrary notwithstanding. A Refusal Notice may only be accepted in
whole, not in part. If Tenant rejects, or is deemed to have rejected, Landlord's
offer with  respect  to the Right of First  refusal,  Landlord  shall be free to
lease the Remaining  Basement  Space to any party upon any terms and  conditions
that Landlord may determine  from time to time during the Term,  with no further
obligation to Tenant under this Section with respect to the  Remaining  Basement
Space.

          17.  Section 4.8 of the  original  Lease is modified as of the date of
this Sixth  Amendment to Lease Agreement to provide Tenant with ninety (90) days
following  Tenant's  receipt of  Landlord's  Statement  in which to dispute  the
correctness  of such  Statement.  Within  ten  (10)  business  days  of  request
therefore  (such tenth day is referred to herein as "Document  Delivery  Date"),
Landlord shall furnish supporting  documentation  reasonably requested by Tenant
in respect of the information reflected on Landlord's Statement.  Landlord shall
have no liability for failing to timely deliver the supporting  documentation by
the Document  Delivery  Date,  except that upon such  failure,  Tenant's time in
which to dispute Landlord's  Statement shall be extended by one (1) day for each
day during the period between the Document Delivery Date and the delivery of the
supporting documentation.

          18. The covenants,  agreements, terms and conditions contained in this
Agreement  shall bind and inure to the benefit of the  parties  hereto and their
respective legal successors and assigns.

          19.  This  Amendment  may not be changed  orally,  but only by writing
signed by the party against which the enforcement thereof is sought.

          20. Except as expressly modified by this Agreement,  the Lease and all
the covenants,  agreements,  terms and  conditions  thereof shall remain in full
force and effect and are hereby in all respects ratified and confirmed.

          21.  (a)  Tenant  shall  have the  option  to  include  as part of the
Premises,  the Remaining  Basement Space pursuant to the terms of the Lease,  as
amended hereby.

          (b)  Any  such  option  shall  be   exercised  by  a  written   notice
(hereinafter called the "Expansion Notice") from Tenant to Landlord given at any
time prior to the date Landlord delivers to Tenant the notification  required in
Section 2.7 of the  Original  Lease with  respect to the Right of First  Refusal
(such notification hereinafter referred to as "Refusal Notice").

          (c) In the event that Tenant shall give Landlord the Expansion Notice,
Tenant shall be deemed to have irrevocably agreed to have the Remaining Basement
Space added to and included in the Premises effective as of the thirtieth (30th)
day after the delivery of the Expansion Notice (the "Inclusion Date").

          (d) In the even that  Tenant  shall  properly  exercise  its option in
accordance with the provisions hereof,  then in such event,  effective as of the
Inclusion Date:

               (i) The  Remaining  Basement  Space shall be deemed  added to and
     included in the Premises for the period  commencing on the  Inclusion  Date
     and ending on the Expiration Date (as such date may be extended pursuant to
     the terms of the Lease,  as amended  hereby).  The  inclusion of such space
     shall be on all the terms and subject to the  conditions  of the Lease,  as
     amended hereby (other than Section 6 of the Original Lease, as amended) and
     on such additional terms and conditions as is hereinafter set forth in this
     Section 21. Tenant shall use the Remaining  Basement Space  exclusively for
     storage and  otherwise in compliance  with the terms and  conditions of the
     Lease, as modified herein;

               (ii) Fixed Rent for the Remaining  Basement Space shall be at the
     annual  rate  of  $4.00  per  square   foot,   payable  in  equal   monthly
     installments.

               (iii) Tenant,  at its sole cost and expense,  shall cause to have
     all electrical  uses of the Remaining  Basement Space connected to Tenant's
     separate electrical meter;

               (iv)  Landlord and Tenant shall execute an amendment to the Lease
     setting forth without  limitation the exercise of the expansion option, the
     inclusion of the Remaining  Basement  Space in the Premises,  the Inclusion
     Date and other appropriate items.

          (e)  Tenant  agrees  to accept  the  Remaining  Basement  Space in its
condition and state of repair  existing as of the Inclusion Date and understands
and agrees that Landlord  shall not be required to perform any work,  supply any
materials  or incur any  expense  to prepare  such  space for Tenant  occupancy.
Notwithstanding the foregoing,  in the event that Tenant exercises its expansion
right as  contemplated  by this  Section  and as of the  date of such  Expansion
Notice  is given,  the  remaining  Term of the Lease is not less than  three (3)
years (including all renewal options which have been exercised),  Landlord shall
provide an allowance ("Expansion Basement Allowance") in an amount not to exceed
the lesser of (1) $2.58 per square foot  calculated  for the Remaining  Basement
Space so leased by Tenant pursuant to this Section ("Leased  Expansion  Space"),
or (2) Tenant's  actual costs in performing  certain work  ("Expansion  Basement
Work").  The Expansion  Basement  Work shall  consist  solely of: (i) erecting a
chain link fence ar ound the  portion of the Leased  Expansion  Space,  and (ii)
installing  lighting in the Leased Expansion Space. The Expansion  Basement Work
shall be of like  nature and  quality of such items  currently  existing  in the
basement. All Expansion Basement Work shall be performed by Tenant in a good and
workmanlike  manner, in compliance with all federal,  sate,  municipal and other
statutes, laws, ordinances,  regulations, rules and requirements relating to the
Building, in accordance with all standards established by Landlord and otherwise
in compliance  with the terms and conditions of the Lease,  as modified  hereby.
Provided  Tenant is not in default of the Lease,  as amended  hereby at the time
payment is due by Landlord,  Landlord shall pay to Tenant the Expansion Basement
Allowance  within thirty (30) days after  Landlord's  receipt of (x) notice that
the Expansion Basement work has been completed,  (y) submission to Landlord of a
complete and final release and lien waiver with respect to the Building executed
by all  partie s with  legal  standing  to file a lien,  and (z)  submission  to
Landlord of all invoices for the work so  performed  and other items  reasonably
requested.

          (f) Tenant's expansion option pursuant to this Section 21 shall expire
and be of no further force and effect as of the date Landlord delivers to Tenant
the Refusal Notice, but only as to the basement space identified in said Refusal
Notice.

          (g) The  termination  of the  Lease,  as  amended  hereby  shall  also
terminate  Tenant's  option  pursuant to this Section 21 whether or not the same
shall have been  exercised.  Nothing  contained  in this Section  shall  prevent
Landlord from  exercising any right or action granted to or reserved by Landlord
in the Lease,  as amended  hereby to  terminate  the Lease,  as amended  hereby.
Tenant's  option set forth in this  Section 21 may not be severed from the Lease
or separately sold,  assigned or transferred and is only exercisable by Dialogic
Corporation or a successor corporation.

          (h)  Tenant  shall  have no right to  exercise  the  expansion  option
pursuant to this  Section 21 if: (i) the named  Tenant has assigned the Lease or
has at any time  subleased,  in the aggregate,  more than fifty percent (25%) of
the  Premises,  or (ii) Tenant  shall be in default  hereunder  and such default
shall not have been cured at the time of the  exercise of its option or, if such
default occurs after Tenant's attempted leasing, as of the Inclusion Date.

<PAGE>
          IN WITNESS WHEREOF,  the parties hereto have here onto set their hands
and seals or caused their presence to be signed by its proper corporate officers
and caused its proper  corporate  seal to be here onto affixed,  the day and the
year first above written.


                                   THE MUTUAL LIFE INSURANCE
WITNESS:                           COMPANY OF NEW YORK
/s/
___________________                By:    /s/_________________________
                                   Name:  Debra Kloper, Vice President
 


WITNESS:                          DIALOGIC CORPORATION
/s/
___________________               By:      /s/__________________________________
                                  Name:    _____________________________________
                                  Its:     _____________________________________