EXHIBIT
10.43





SECOND
AMENDED AND RESTATED GUARANTY





SECOND AMENDED AND RESTATED
GUARANTY dated as of December 22, 2009 made by the undersigned
(individually, or if more than one, collectively, the “Guarantor”) in favor
of JPMorgan Chase Bank, N.A., and/or any of its subsidiaries or affiliates
(individually or collectively, as the context may require, the “Bank”).





PRELIMINARY
STATEMENTS:  The Bank has entered, or may from time to time
enter, into agreements or arrangements with Avistar Communications Corporation,
a Delaware corporation (the “Borrower”), providing
for credit extensions or financial accommodation to the Borrower of any kind
whatsoever including, without limitation, the making of loans, advances or
overdrafts, whether or not secured, discount or purchase of notes, securities or
other instruments or property, creation of acceptances, issuance or confirmation
of letters of credit, guaranties or indemnities, entering into foreign exchange
or precious metals contracts or interest rate or currency swap or protection
agreements, entering into any other derivative transactions under any ISDA
Master Agreement or similar agreements between the Bank and the Borrower, or any
other kind of lease, contract or agreement under which the Borrower may be
indebted to the Bank in any manner (all of the foregoing agreements or
arrangements being the “Facilities” and any
writing or record evidencing, supporting, securing, or delivered in connection
with a Facility, including but not limited to this Guaranty, and including as
may subsequently be renewed, extended, amended,  modified, substituted
and/or replaced, being a “Facility
Document”).





THEREFORE, in order to induce
the Bank to extend credit or give financial accommodation under the Facilities,
the Guarantor agrees (and if more than one, jointly and severally agrees) as
follows:





Amendment
and Restatement.  This Guaranty amends and restates in its
entirety the Amended and Restated Guaranty dated as of December 22, 2008, as
amended, by which the Guarantors, jointly and severally, guaranteed, among other
things, the Borrower’s obligations to the Bank under that certain Amended and
Restated Revolving Credit Promissory Note (Libor/Prime) dated as of December 22,
2008 to the order of the Bank in a maximum principal amount of $10,000,000 (as
amended by the first and second amendments thereto, the “Original
Note”).





Guaranty
of Payments.  For value received and in consideration of the
Facilities extended by the Bank the Guarantor unconditionally and irrevocably
guarantees to the Bank (a) performance and observance of every agreement and
condition contained in any Facility Document to be performed or observed by the
Borrower, and (b) payment of all sums now owing or which may in the future be
owing by the Borrower under the Facilities, when the same are due and payable,
whether on demand, at stated maturity, by acceleration or otherwise, and whether
for principal, interest, fees, expenses, indemnification or otherwise (the
“Liabilities”).  The
Liabilities include, without limitation, interest accruing after the
commencement of a proceeding under bankruptcy, insolvency or similar laws of any
jurisdiction at the rate or rates provided in the Facility
Documents.


This Guaranty is a guaranty of payment
and performance and not of collection only.  The Bank shall not be
required to exhaust any right or remedy or take any action against the Borrower
or any other person or entity or any collateral.  The Guarantor agrees
that, as between the Guarantor and the Bank, the Liabilities may be declared to
be due and payable for the purposes of this Guaranty notwithstanding any stay,
injunction or other prohibition which may prevent, delay or vitiate any
declaration as regards the Borrower and that in the event of a declaration or
attempted declaration, the Liabilities shall immediately become due and payable
by the Guarantor for the purposes of this Guaranty.





The Guarantor shall pay the Liabilities
by the seventh (7th) day on which commercial banks are not authorized or
required to close in New York City (a “Banking Day”) after
the Bank’s demand for payment thereof (or if such demand is accompanied by
notice from the Bank, or the Bank thereafter delivers notice, that the value of
collateral securing the Liabilities is less than the amount of the Liabilities,
on the second (2nd)
Banking Day after delivery of such notice) (the “Due
Date”).  Upon the Bank’s making demand for
payment of the Liabilities but prior to the Due Date, the Guarantor shall have
the right (but not the obligation) to execute and deliver to the Bank a note
sale agreement substantially in the form of Exhibit A hereto (the
“Loan Sale
Agreement”) together with payment of the “Note Purchase Price”
(as defined therein) in immediately available funds, whereupon the obligations
of the Guarantor hereunder shall terminate (but subject to reinstatement as
provided below).





UCN
006754857000
 Facility
ID 198245263
 1











Notwithstanding anything to the
contrary set forth herein, for purposes of this Guaranty the Facilities of the
Borrower guaranteed shall be limited to those arising under and in connection
with the Second Amended and Restated Revolving Promissory Note (Libor/Prime)
dated as of December 22, 2009 by the Borrower in favor of the Bank in the
maximum principal amount of $11,250,000, as amended, restated or otherwise
modified from time to time (the “New Note”) or any
other “Facility
Document” (as defined in the Note), together with every renewal,
extension, amendment, modification, substitution and/or replacement thereof,
each of which together with this Guaranty and any other writing or record
evidencing, supporting, securing or delivered in connection with the foregoing
shall be considered a Facility Document for purposes of this
Guaranty.





Guaranty
Absolute.  The Guarantor guarantees that the Liabilities shall
be performed and paid strictly in accordance with the terms of the
Facilities.  The liability of the Guarantor under this Guaranty is
absolute and unconditional irrespective of:  (a) any change in the
amount, time, manner or place of payment of, or in any other term of, all or any
of the Facility Documents or Liabilities, or any other amendment or waiver of or
any consent to departure from any of the terms of any Facility Document or
Liability; (b) any release or amendment or waiver of, or consent to departure
from, any other guaranty or support document, or any exchange, release or
non-perfection of any collateral (any change in the value of any collateral or
failure of the Bank to monitor the value of any collateral), for all or any of
the Facility Documents or Liabilities; (c) any present or future law, regulation
or order of any jurisdiction (whether of right or in fact) or of any agency
thereof purporting to reduce, amend, restructure or otherwise affect any term of
any Facility Document or Liability; (d) without being limited by the foregoing,
any lack of validity or enforceability of any Facility Document or Liability;
and (e) any other defense, setoff or counterclaim whatsoever (in any case,
whether based on contract, tort or any other theory) with respect to the
Facility Documents or the transactions contemplated thereby which might
constitute a legal or equitable defense available to, or discharge of, the
Borrower or a guarantor.





Guaranty
Irrevocable.  This Guaranty is a continuing guaranty of all
Liabilities now or hereafter existing under the Facilities and shall remain in
full force and effect until payment in full of all Liabilities and other amounts
payable under this Guaranty and until the Facilities are no longer in effect or,
if earlier, when the Guarantor has given the Bank written notice that this
Guaranty has been revoked; provided that any
notice under this Section shall not release the Guarantor from any Liability,
absolute or contingent, existing prior to such notice.  Such notice
shall be effective only after the Bank’s actual receipt of the notice at its
address set forth below, and the Bank shall have had a reasonable time to act
upon such notice at each of its offices or departments responsible for the
Facilities.





Reinstatement.  This
Guaranty shall continue to be effective or be reinstated, as the case may be, if
at any time (i) any payment of any of the Liabilities is rescinded or must
otherwise be returned by the Bank on the insolvency, bankruptcy or
reorganization of the Borrower or otherwise, all as though the payment had not
been made or (ii)  the Loan Sale Agreement  shall be held invalid
or unenforceable in whole or in any part..





Subrogation.  The
Guarantor shall not exercise any rights against the Borrower which it may
acquire by way of subrogation, by any payment made under this Guaranty or
otherwise, until all the Liabilities have been paid in full and the Facilities
are no longer in effect.  If any amount is paid to the Guarantor on
account of subrogation rights under this Guaranty at any time when all the
Liabilities have not been paid in full, the amount shall be held in trust for
the benefit of the Bank and shall be promptly paid to the Bank to be credited
and applied to the Liabilities, whether matured or unmatured or absolute or
contingent, in accordance with the terms of the Facilities.


UCN
006754857000
 Facility
ID 198245263
 2


Subordination.  Without
limiting the Bank’s rights under any other agreement, any liabilities owed by
the Borrower to the Guarantor in connection with any extension of credit or
financial accommodation by the Guarantor to or for the account of the Borrower,
including but not limited to interest accruing at the agreed contract rate after
the commencement of a bankruptcy or similar proceeding, are hereby subordinated
to the Liabilities, and such liabilities of the Borrower to the Guarantor, if
the Bank so requests, shall be collected, enforced and received by the Guarantor
as trustee for the Bank and shall be paid over to the Bank on account of the
Liabilities but without reducing or affecting in any manner the liability of the
Guarantor under the other provisions of this Guaranty.





Representations
and Warranties.  The Guarantor represents and warrants
that:





(a)           this
Guaranty constitutes the legal, valid and binding obligation of the Guarantor,
enforceable against the Guarantor in accordance with its terms, except as the
enforcement hereof and thereof may be limited by bankruptcy, insolvency, or
other similar laws affecting the enforcement of creditors’ rights generally and
subject to the applicability of general principles of equity;


(b)           the
execution, delivery and performance by the Guarantor of this Guaranty and all
other documents contemplated hereby or thereby, do not and will not (i) conflict
with or constitute a breach of, or default under, or require any consent under,
or result in the creation of any lien, charge or encumbrance upon the property
or assets of the Guarantor pursuant to any other agreement or instrument (other
than any pledge of or security interest granted in any collateral pursuant to
any Facility Document) to which the Guarantor is a party or is bound or by which
its properties may be bound or affected; or (ii) violate any provision of any
law, rule, regulation (including, without limitation, Regulation U of the
Federal Reserve Board), order, writ, judgment, injunction, decree, determination
or award presently in effect having applicability to the Guarantor;


(c)           no
consent, approval or authorization of, or registration, declaration or filing
with, any governmental authority or other person or entity is required as a
condition to or in connection with the due and valid execution, delivery and
performance by the Guarantor of this Guaranty;


(d)           there
are no actions, suits, investigations or proceedings pending or threatened at
law, in equity, in arbitration or by or before any other authority involving or
affecting:  (i)  the Guarantor that, if adversely
determined, are likely to have a material adverse effect on the prospects or
condition of the Guarantor; (ii) any material part of the assets or properties
of the Guarantor or any part of the collateral (if any) under any Facility
Document; or (iii) any of the transactions contemplated in this
Guaranty.  There are currently no material judgments entered against
the Guarantor and the Guarantor is not in default with respect to any judgment,
writ, injunction, order, decree or consent of any court or other judicial
authority, which default is likely to have or has had a material adverse effect
on the prospects or condition of the Guarantor;


(e)           in
executing and delivering this Guaranty, the Guarantor has (i) without reliance
on the Bank or any information received from the Bank and based upon such
documents and information it deems appropriate, made an independent
investigation of the transactions contemplated hereby and the Borrower, the
Borrower’s business, assets, operations, prospects and condition, financial or
otherwise, and any circumstances which may bear upon such transactions, the
Borrower or the obligations and risks undertaken herein with respect to the
Liabilities; (ii) adequate means to obtain from the Borrower on a continuing
basis information concerning the Borrower and the Bank has no duty to provide to
the Guarantor any such information; (iii) full and complete access to the
Facility Documents and any other documents executed in connection with the
Facility Documents; (iv) not relied and will not rely upon any representations
or warranties of the Bank not embodied herein or any acts heretofore or
hereafter taken by the Bank (including but not limited to any review by the Bank
of the affairs of the Borrower), and (v) determined that this Guaranty will
benefit the Guarantor directly or indirectly;


(f)           in
the event that the Guarantor is a partnership, limited liability partnership,
corporation or limited liability company, the Guarantor also represents and
warrants (i) that it is duly organized, validly existing and in good standing
under the laws of the jurisdiction of its incorporation or organization, (ii)
that it has all requisite power and authority to execute, deliver and perform
its obligations under this Guaranty, and (iii) that the execution, delivery and
performance of this Guaranty is in furtherance of its organizational purposes,
and has been presented to and approved by its partners, directors, shareholders
or members, as applicable; and


(g)           in
the event that the Guarantor is a trust, the Guarantor also represents and
warrants that (i) it is a duly constituted and validly existing trust, (ii) the
Guarantor has delivered to the Bank a true, complete and accurate copy of the
agreement pursuant to which it has been organized and all amendments and
modifications thereto, and (iii) the trustees of the Guarantor signing this
Guaranty have the legal capacity and full power and authority to execute,
deliver, and perform their obligations under, and to bind the Guarantor to
perform its obligations under, this Guaranty, and to execute and deliver any and
all documents and instruments in connection herewith.


UCN
006754857000
 Facility
ID 198245263
 3








Defaults.    Each
of the following is an event of default hereunder:


(a)           The
Guarantor (i) shall fail to pay when due any of its indebtedness
(including, but not limited to, indebtedness for borrowed money) or any interest
or premium thereon in an aggregate amount of at least five hundred thousand
dollars ($500,000) or (ii) the Guarantor shall default or otherwise fail to
perform any agreement to which the Guarantor is party or by which it is bound
which results in the holder(s) of indebtedness having the right, whether or not
exercised, to accelerate the maturity thereof in an aggregate amount of at least
five hundred thousand dollars ($500,000);


(b)           (i) the
Guarantor is involved in a proceeding which may result in a forfeiture of all or
a substantial part of the Guarantor’s assets or (ii) a final,
non-appealable judgment is entered against the Guarantor for the payment of in
an aggregate amount of at least two million
dollars ($2,000,000);


(c)           there
is, in the opinion of the Bank, a material adverse change in the business,
prospects or financial condition of the Guarantor;


(d)           without
the prior written consent of the Bank, the Guarantor incurs or permits to exist
(i) any debt for borrowed money other than debt for borrowed money owing to
the Bank or listed on the Guarantor’s financial statement dated April 20
2006 (the “Financial
Statement”) and any refinancing of such debt or (ii) other debt to the
extent that the total amount thereof when added together with the total amount
of the Borrower’s guarantees and contingent liabilities referred to in
clause (ii) of the immediately following paragraph (e) is less than or
equal toseven million dollars ($7,000,000); and


(e)           the Guarantor
guarantees or otherwise becomes contingently liable for the debts or other
obligations of any entity other than (i) any such guaranty or contingent
obligation shown on the Financial Statementand
(ii) guarantees and contingent obligations incurred after the date of the
Financial Statement to the extent that the total amount thereof when added
together with the total amount of debt referred to in clause (ii) of the
immediately preceding paragraph (d) is less than or equal toseven million
dollars ($7,000,000).





Remedies
Generally.  The rights, powers and remedies granted to the Bank
in this Guaranty are cumulative and in addition to any rights, powers and
remedies to which the Bank may be entitled either by operation of law or in
equity or pursuant to any other document or instrument delivered or from time to
time to be delivered to the Bank in connection with the Facilities.





Setoff.  The
Guarantor agrees that, in addition to (and without limitation of) any right of
setoff, banker’s lien or counterclaim the Bank may otherwise have, the Bank
shall be entitled, at its option, to offset balances (general or special, time
or demand, provisional or final) held by it for the account of the Guarantor at
any of the Bank’s offices, in U.S. dollars or in any other currency, against any
amount payable by the Guarantor under this Guaranty which is not paid when due
(regardless of whether such balances are then due to the Guarantor), in which
case it shall promptly notify the Guarantor thereof; provided that the
Bank’s failure to give such notice shall not affect the validity
thereof.





Formalities.  The
Guarantor waives presentment, notice of dishonor, protest, notice of acceptance
of this Guaranty or incurrence of any Liability and to the extent not prohibited
by applicable law any other formality with respect to any of the Liabilities or
this Guaranty.





Amendments
and Waivers.  No amendment or waiver of any provision of this
Guaranty, nor consent to any departure by the Guarantor therefrom, shall be
effective unless it is in writing and signed by the Bank, and then the waiver or
consent shall be effective only in the specific instance and for the specific
purpose for which given.  No failure on the part of the Bank to
exercise, and no delay in exercising, any right under this Guaranty shall
operate as a waiver or preclude any other or further exercise thereof or the
exercise of any other right.


UCN
006754857000
 Facility
ID 198245263
 4


Expenses.  The
Guarantor shall reimburse the Bank on demand for all costs, expenses and charges
(including without limitation fees and charges of external legal counsel for the
Bank and costs allocated by its internal legal department) incurred by the Bank
in connection with the preparation, performance or enforcement of this
Guaranty.  The obligations of the Guarantor under this Section shall
survive the termination of this Guaranty.





Assignment.  This
Guaranty shall immediately be binding on, and shall inure to the benefit of the
Guarantor, the Bank and their respective heirs, successors and assigns; provided that the
Guarantor may not assign or transfer its rights or obligations under this
Guaranty.





Captions.  The
headings and captions in this Guaranty are for convenience only and shall not
affect the interpretation or construction of this Guaranty.





Governing
Law, Waiver of Jury Trial, Etc.  THIS GUARANTY SHALL BE GOVERNED BY
AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK WITHOUT
REGARD TO THE CONFLICT OF LAWS PRINCIPLES, AND WITH THE LAWS OF THE UNITED
STATES OF AMERICA AS APPLICABLE.  THE GUARANTOR CONSENTS TO THE
NONEXCLUSIVE JURISDICTION AND VENUE OF THE STATE OR FEDERAL COURTS LOCATED IN
THE CITY OF NEW YORK.  SERVICE OF PROCESS BY THE BANK IN CONNECTION
WITH ANY SUCH DISPUTE SHALL BE BINDING ON THE GUARANTOR IF SENT TO THE GUARANTOR
BY REGISTERED MAIL AT THE ADDRESS SPECIFIED BELOW OR AS OTHERWISE SPECIFIED BY
THE GUARANTOR FROM TIME TO TIME.THE GUARANTOR WAIVES ANY RIGHT THE
GUARANTOR MAY HAVE TO JURY TRIAL IN ANY ACTION RELATED TO THIS GUARANTY OR THE
TRANSACTIONS CONTEMPLATED HEREBY AND FURTHERWAIVES ANY RIGHT TO INTERPOSE ANY
COUNTERCLAIM RELATED TO THIS GUARANTY OR THE TRANSACTIONS CONTEMPLATED HEREBY IN
ANY SUCH ACTION.  TO THE EXTENT THAT THE GUARANTOR HAS OR HEREAFTER
MAY ACQUIRE ANY IMMUNITY FROM JURISDICTION OF ANY COURT OR FROM ANY LEGAL
PROCESS (WHETHER FROM SERVICE OR NOTICE, ATTACHMENT PRIOR TO JUDGMENT,
ATTACHMENT IN AID OF EXECUTION OF A JUDGMENT, EXECUTION OR OTHERWISE), THE
GUARANTOR HEREBY IRREVOCABLY WAIVES SUCH IMMUNITY IN RESPECT OF ITS OBLIGATIONS
UNDER THIS GUARANTY.








Integration;
Effectiveness.  This Guaranty alone sets forth the entire
understanding of the Guarantor and the Bank relating to the guarantee of the
Liabilities and constitutes the entire contract between the parties relating to
the subject matter hereof and supersedes any and all previous agreements and
understandings, oral or written, relating to the subject matter
hereof.  This Guaranty shall become effective when it shall have been
executed and delivered by the Guarantor to the Bank.  Delivery of an
executed signature page of this Guaranty by telecopy shall be effective as
delivery of a manually executed signature page of this Guaranty.





The
rest of this page is intentionally blank.





UCN
006754857000
 Facility
ID 198245263
 5


IN
WITNESS WHEREOF, the Guarantor has caused this Guaranty to be duly executed and
delivered as of the date first above written.








Address
for notices to the Bank:





JPMorgan
Chase Bank, N.A.


Private
Bank Credit


Attn:Arn Welles


345 Park
Avenue, Floor 04


New York,
NY 10154-0004


Telecopier:  (212)
464-2531


Telephone:  (212)
464-1883





With a
courtesy copy to





JPMorgan
Chase Bank, N.A.


Attn:  Nancy
A. Sheppard


560
Mission Street, 19th
floor


San
Francisco, CA 94105


Telecopier:  (415)
315-8272


Telephone:  (415)
315-8285








/s/ Gerald J.
Burnett


Gerald
J. Burnett





Address
for notices:


202
Camino Al Lago


Atherton,
CA 94027


Telecopier:  (650)
322-2060


Telephone:  (650)
322-2060








Gerald
J. Burnett and Marjorie J. Burnett , as Trustee for


The
Gerald J. Burnett and Marjorie J. Burnett Revocable Trust








By:          /s/Gerald J.
Burnett


Gerald J. Burnett





By:          /s/Majorie J.
Burnett


Marjorie J. Burnett











Address
for notices:


c/o
Gerald J. Burnett


202
Camino Al Lago


Atherton,
CA 94027


Telecopier:  (650)
322-2060


Telephone:  (650)
322-2060





UCN
006754857000[Signature Page of
Second Amended and Restated Guaranty]
 Facility
ID 198245263


State of
_________                                )


) ss.:


County
      of ________
            )





On the ____ day of December in the year
2009, before me, the undersigned, personally appeared Gerald J. Burnett, personally
known to me or proved to me on the basis of satisfactory evidence to be the
individual whose name is subscribed to the within instrument and acknowledged to
me that he/she executed the same in his/her capacity, and that by his/her
signature on the instrument, the individual, or the person upon behalf of which
the individual acted, executed the instrument.





____________________________________


Notary Public


State
      of _________
            )


) ss.:


County
      of ________
            )





On the ____ day of December in the year
2009, before me, the undersigned, personally appeared Marjorie J. Burnett,
personally known to me or proved to me on the basis of satisfactory evidence to
be the individual whose name is subscribed to the within instrument and
acknowledged to me that he/she executed the same in his/her capacity, and that
by his/her signature on the instrument, the individual, or the person upon
behalf of which the individual acted, executed the instrument.





____________________________________


Notary Public





UCN
006754857000[Signature Page of
Second Amended and Restated Guaranty]
 Facility
ID 198245263


Exhibit
A





FORM OF
NOTE SALE AGREEMENT


UCN
006754857000
 Facility
ID 198245263