<PAGE>
                                                                     Exhibit 4.2

                                    AGREEMENT


         THIS AGREEMENT made and entered into as of the 14th day of April, 1995,
by and among RADVISION LTD., an Israeli company of 8 Hanechoshet Street, Tel
Aviv 69710, Israel (the "Company") and RAD DATA COMMUNICATIONS LTD., an Israeli
company with its principal office at 8 Hanechoshet Street, Tel Aviv 69710,
Israel (the "Purchaser") and Yehuda Zisapel and Zohar Zisapel of 8 Hanechoshet
Street, Tel Aviv 69710, Israel (jointly and severally, the "Present
Shareholders").

                              W I T N E S S E T H :

         WHEREAS, the Company is and will be engaged in the business of
developing, manufacturing and marketing of products for video conferencing (the
"Field"); and

         WHEREAS, the Company desires to issue and sell, and the Purchaser
desires to purchase ordinary shares, par value One New Israeli Shekel (NIS
1.00), of the Company ("Ordinary Shares"),

         NOW, THEREFORE, in consideration of the premises and the mutual
covenants and conditions herein contained, the Company and the Purchaser hereby
agree as follows:

                                    SECTION 1
                         ISSUANCE AND PURCHASE OF SHARES

         1.1 The Purchaser undertakes to invest in the Company the amount of
Seven Hundred Ten Thousand and Thirty US Dollars (US$ 710,030) (hereinafter, the
"Investment Amount") on the Closing Date as defined in Section 2 hereinbelow.
All amounts will be deposited in US dollars or their equivalent in NIS to the
Company's account no. 377906 at Bank Hapoalim B.M., Hadar Yosef Branch (610).

         1.2 In consideration for and subject to the execution of the
investment, the Company shall issue on the Closing Date three thousand five
hundred and fifteen (3,515) ordinary shares (hereinafter, the "Shares") to the
Purchaser. The Company shall not be obligated to issue any shares whatsoever
before the full Investment Amount is received by it. The Shares, when issued,
will have been validly issued, fully paid and non-assessable, and will be free
of any liens or encumbrances.

         1.3 The Investment Amount is part of a total amount of approximately US
$4,930,000 (hereinafter, the "Total Investment") intended to be raised by the
Company from the Purchaser as well as from other investors (hereinafter, the
"Other Purchasers") as set forth in Exhibit 1 attached hereto. In consideration
for the Total Investment, the Company will issue 24,453 Ordinary Shares, par
value 1.- NIS each. After all said shares have been issued, the ownership of the
Company will be as set forth in Exhibit 1.

                                    SECTION 2
                                  CLOSING DATE
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         The purchase of the Shares by the Purchaser shall take place on April
25, 1995 (the "Closing"). The date of the Closing is referred to as the "Closing
Date" in this Agreement.

                                    SECTION 3
                  REPRESENTATIONS AND WARRANTIES OF THE COMPANY

         The Company and the Present Shareholders hereby represent and warrant
to the Purchaser the facts hereinafter set forth in this Section 3.

        3.1 CORPORATE POWER. As of the date hereof and as of the Closing, the
Company has and will have all requisite corporate power to enter into and to
perform this Agreement.

        3.2 SUBSIDIARIES. The Company has a wholly owned U.S. subsidiary,
RADVISION Inc. in New Jersey. The Company has no other subsidiaries and does not
otherwise own, of record or beneficially, any capital stock or equity interest
in any other corporation, association or business entity.

         3.3 ORGANIZATION AND STANDING. The Company is a corporation duly
organized and existing under the laws of the State of Israel and is in good
standing under such laws. The Company has requisite corporate power to own and
operate its properties and assets, and to carry on its business as presently
conducted. The Memorandum of Association and Articles of Association and all
amendments to date of the Company are attached hereto as EXHIBITS "3.3A" AND
"3.3B."

         3.4 CAPITALIZATION. The Company's authorized capital is sixty thousand
(60,000) Ordinary Shares. The Company's issued capital stock immediately prior
to the Closing date shall consist of twenty thousand seven hundred thirty-two
(20,732) Ordinary Shares, all of which are duly authorized, validly issued and
free of any liens or encumbrances. Out of the issued share capital, thirteen
thousand eight hundred sixty (13,860) shares are fully paid and six thousand
eight hundred seventy-two (6,872) shares are partially paid. All shares are
non-assessable, and to the best of the Company's knowledge and belief, are
beneficially owned by their holders of record. There are no preemptive,
conversion or other rights, options, or agreements granted or issued by, or
binding upon, the Company or the shareholders which entitle any person, firm or
corporation to purchase or acquire any shares of the Company's capital stock,
except as set forth in this Agreement and in particular, in Sections 3.21, 3.22
and 3.23.

         3.5 AUTHORIZATION. All corporate actions on the part of the Company and
its directors and shareholders, required for the authorization, execution,
delivery and performance by the Company of this Agreement and the consummation
of the transactions contemplated herein have been, or will be executed, upon
signature of this Agreement. ThisAgreement is and will be valid and binding
obligations of the Company, enforceable in accordance with its terms. The
execution, delivery and performance by the Company of this Agreement, and
compliance therewith, and the consummation of the transactions contemplated by
this Agreement will not result in any violation of and will not conflict with,
or result in a breach of any of the terms of, or constitute a default under, any
document to which the Company is or will be a party or by which it is or will be
bound, or result in the creation of any mortgage, pledge, lien or encumbrance or
charge upon any of the properties or assets of the Company. To the best of the
Company's knowledge, no third party's consent is required for the Company to
become a party to this


                                       2
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Agreement. Immediately after the Closing Date, the Company will inform all
governmental authorities that require to be reported of changes in equity,
including, but not limited to the Israel Investment Center and the Office of the
Chief Scientist of the execution of this Agreement.

         3.6 OUTSTANDING DEBT. Except as set forth in the Schedule of Exceptions
attached hereto as EXHIBIT "A" ("Schedule of Exceptions"), the Company has no
outstanding indebtedness for borrowed money and is not a guarantor of any debt
or obligation of another. There exists no default by the Company under the
provisions of any agreement or other instrument evidencing or relating to any
indebtedness or obligation.

         3.7 ABSENCE OF UNDISCLOSED LIABILITIES. Except as set forth in the
Schedule of Exceptions, the Company has no material liability of any nature,
direct or indirect, absolute or contingent, not adequately reserved against,
excluding any liabilities related to damage which may have been caused by its
products or are related to sales of said products (unless the Company knows or
should have known of such damages or liabilities). The Company has paid, or has
made adequate provisions for the payment of, all taxes, interest, penalties,
assessments or deficiencies owing by it to any taxing authority.

         3.8 ABSENCE OF CERTAIN CHANGES. Since December 31, 1994, the business
of the Company has at all times been conducted in the ordinary course. There has
not been any event or condition of any character which has materially adversely
affected the Company's business, prospects or plans.

         3.9 CONTRACTS AND CONTRACTUAL ARRANGEMENTS. The Company is a party to
several material agreements, all of which are described in the Schedule of
Exceptions attached hereto. Each of such agreements is in full force and effect
and, to the Company's knowledge, no party thereto is in breach thereof. The
Company is of the opinion that it receives services from affiliated companies
for fair consideration as described in the Schedule of Exceptions attached
hereto. The Company is not obligated to receive services from said affiliated
companies.

        3.10 INDEBTEDNESS OF OR TO SHAREHOLDERS, ETC.; CONFLICTS OF INTEREST.

                (a) Except as set forth in the Schedule of Exceptions, none of
the Company's shareholders, directors, officers or employees or any of their
affiliates or families is indebted to the Company and the Company has no debt to
any of them except for accrued wages for the current period.

                (b) Except as set forth in the Schedule of Exceptions, to the
best of the Company's knowledge, none of the Company's directors, officers,
employees or consultants, or their affiliates or families, directly or
indirectly, own any material interest in any entity which is a competitor of the
Company.

         3.11 LITIGATION; INSOLVENCY PROCEEDINGS. To the best of the Company's
knowledge and belief, there are no pending or threatened actions, suits,
proceedings or any investigations against or affecting the Company involving the
possibility of any judgment or liability which would adversely affect its
business.

         3.12 INSURANCE. The Company maintains insurance through RAD-Bynet
insurance policies, adequately covering the perils normally insured against by
companies similarly situated.


                                       3
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All policies of insurance maintained by the Company are attached hereto as
EXHIBIT "3.12." To the best of the Company's knowledge, all such policies are in
full force and effect.

         3.13 TITLE TO PROPERTIES; LIENS AND ENCUMBRANCES. Except as set forth
in the Schedule of Exceptions, the Company owns, or holds under lease, all real
and personal property used by it in its business. All property owned by the
Company (all of which is listed on EXHIBIT "3.13" hereto) is so owned free and
clear of all mortgages, pledges, liens or charges.

         3.14 LEASES. EXHIBIT "3.14" hereto contains a correct and complete list
and description (including the amount of rents) of all leases under which the
Company leases property, real or personal.

         3.15 BUSINESS OF THE COMPANY. The Company has no knowledge of (i) the
existence of any pending or planned patent, or any statute, rule, law,
regulation, standard or codes which would materially adversely affect the
condition, financial or otherwise, or the business operations, of the Company;
or (ii) the existence of any other factor which would materially adversely
affect the financial condition, or the operations, of the Company.

         3.16 COMPLIANCE WITH OTHER INSTRUMENTS. The Company is not in violation
of the terms of its Memorandum or Articles of Incorporation, and it is not in
violation of the terms of any judgment, decree, order, statute, rule or
regulation to which it is subject.

         3.17 EMPLOYEES. All the key employees of the Company are listed on
EXHIBIT "3.17" hereto. To the best of the Company's knowledge, no such employee
is in violation of any material term of any employment contract, patent
disclosure agreement, non-competition agreement, or any other contract or
agreement or any restrictive covenant or any other obligation to a former
employer relating to the right of any such employee to be employed by the
Company. To date, all payments due to the Company's employees have been paid
regularly. In addition, the Company made all allowances required by law to cover
the amounts due to its employees and/or officers in connection with their
employment and/or termination of employment, as reflected in EXHIBIT "3.20A."

         3.18 DISCLOSURE. This Agreement and the Schedule of Exceptions
delivered to the Purchaser do not contain any material untrue statement and do
not omit to state a material fact necessary in order to make the statements
contained herein not misleading in the light of the circumstances under which
they were made, and such documents represent full disclosure by the Company of
the material facts with respect to the business, prospect and plans of the
Company. The Company confirms that to the date of this Agreement, the Business
Plan dated August, 1994, which was provided to the Purchaser, does not contain
any materially untrue information as far as same relates to the Company itself.
The other information contained therein may have changed since August, 1994.

         3.19 PRODUCTS AND OWNERSHIP. A description of the products is enclosed
as EXHIBIT 3.19. To the best of the knowledge and belief of the Company and as
set forth in the Schedule of Exceptions, the Company possesses, or is proceeding
with due diligence to obtain, all patents, patent rights, trademarks, trademark
names, trade name rights and copyrights the Company believes are necessary to
conduct its business as now being conducted and as planned to be conducted
(without conflict with, or infringement upon, any valid rights of others), the
lack of


                                       4
<PAGE>

which could affect the operations or condition, financial or otherwise, of the
Company. The Company has no knowledge of any infringement by the Company or
claimed infringement upon, or any conflict with, the patent rights, trademarks,
trademark rights, trade names, trade name rights, copyrights, intellectual
property rights or other rights of any person, form or corporation.

         3.20 FINANCIAL STATEMENTS. The audited financial statements of the
Company as of December 31, 1994 are attached hereto as EXHIBIT "3.20A" and
adequately reflect the financial situation of the Company. The unaudited
financial statements of the Company as of February 28, 1995 are attached hereto
as EXHIBIT "3.20B." As of December 31, 1994 to date, the Company did not enter
into any material transaction or undertake any material commitment which was not
in the normal course of business, and there was no material change for the worse
in the Company's position, liabilities and assets.

         3.21 The agreements with the other purchasers will resemble the
Agreement with Purchaser.

         3.22 In the event of any contradiction between this Agreement and the
Inception Agreement, attached hereto as EXHIBIT "3.22." and the current
Memorandum of Association and current Articles of Association, this Agreement
shall prevail.

         3.23 On January 1, 1995, a trust in favor of employees of the Company
and certain employees of the RAD-Bynet group was created. Said Trust Agreement
is attached hereto as EXHIBIT "3.23."

        3.24 As of the date of this Agreement, the directors of the Company are:
Yehuda Zisapel, Zohar Zisapel and Amos Amir.

                                    SECTION 4
                 REPRESENTATIONS AND WARRANTIES OF THE PURCHASER

         The Purchaser represents and warrants to the Company as follows:

         4.1 LEGAL POWER. As of the date hereof and as of the Closing, the
Purchaser has and will have all requisite power to enter into and to perform
this Agreement.

         4.2 EXPERIENCE. The Purchaser has sufficient experience and expertise
to evaluate the suitability of its investment in the Company to its needs and
has the capacity to protect its interests with the purchase of the Shares.

        4.3 INVESTMENT. The Purchaser is acquiring the Shares for investment for
its own account.

        4.4 ACCESS TO DATA. The Purchaser hereby represents that it has had the
full opportunity to discuss management and financial affairs of the Company with
its management and key employees and has had the opportunity to review the
business plan and the Company's facilities. The Purchaser has not been denied
any information that has been requested, and based on the said information has
made a diligent examination of the aspects of the Company's business. The
Purchaser has heretofore received all information that the Purchaser has deemed
necessary and appropriate to enable the Purchaser to evaluate the financial risk
inherent in


                                       5
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making an investment in the shares of the Company and the Purchaser has received
satisfactory and complete information concerning the business and financial
condition of the Company in response to all inquiries in respect thereof. The
Purchaser is aware that the Company has been in the development stage since its
inception in October 1992, that no sales of its products have taken place, and
that due to the short operating history of the Company there can be no assurance
that the Company will attain profitability. Nothing contained in this Section
4.4 shall derogate from the liability of the Company with respect to the
representations and warranties made in Section 3 above.

         4.5 AUTHORIZATION. All corporate or partnership action on the part of
the Purchaser, its respective directors, partners and/or shareholders necessary
for the authorization, execution, delivery, payment and performance by the
Purchaser of this Agreement and the consummation of the transactions
contemplated herein, has been taken.

         4.6 Purchaser has sufficient financial resources to enable it to
fulfill its obligations under this Agreement and commits to make its investment
in the Company as set forth in Section 1 hereinabove.


                                    SECTION 5
                     CONDITIONS OF THE PURCHASER TO CLOSING

         The obligations of the Purchaser at the Closing, as referred to in
Section 1 hereof, are subject to the fulfillment of each of the following
conditions:

         5.1 REPRESENTATIONS AND WARRANTIES CORRECT. The representations and
warranties made by the Company in Section 3 hereof shall be true and correct
when made, and shall be true and correct in all material respects on Closing
with the same force and effect as if they had been made immediately prior to the
Closing and as of such time except for such changes which result from the
obligations of the parties to this Agreement.

         5.2 PERFORMANCE. All covenants, agreements and conditions contained in
this Agreement to be performed or complied with by the Company on or prior to
Closing shall have been performed or complied with in all respects.

        5.3 LEGAL INVESTMENT. At the time of the Closing, the purchase and
issuance of the Shares shall be legally permitted by all laws and regulations to
which the Purchaser and the Company are subject.

         5.4 PROCEEDINGS AND DOCUMENTS. All corporate and other proceedings in
connection with the transactions contemplated hereby and all documents and
instruments incident to such transactions shall have been completed to the
satisfaction (as to substance and form) of the Purchaser.

         5.5 PROPRIETARY INFORMATION AND NON-COMPETITION AGREEMENT. Each of the
Company's employees shall have executed and delivered to the Company an
Employment Agreement, substantially in the form attached hereto as EXHIBIT
"5.5A" or EXHIBIT "5.5B," which agreement contains non-disclosure and
non-competition provisions therein.


                                       6
<PAGE>

         5.6 RETENTION OF KEY EMPLOYEES. All the persons listed in EXHIBIT
"3.17" shall either be employees of the Company as of the Closing and to the
best of the Company's knowledge, have not informed them that they intend to
leave the Company, or if an employee has left the Company or intends to leave
the Company, the latter has notified the Purchaser of same.

         5.7 OPINION OF COMPANY'S COUNSEL. The Purchaser shall have received
from Nehama Sneh, corporate counsel to the Company, a satisfactory opinion in
substantially the form attached as EXHIBIT "5.7."

                                    SECTION 6
                        CONDITIONS OF COMPANY TO CLOSING

         The obligations of the Company at the Closing, as referred to in
Section 1 hereof, are subject to the fulfillment of each of the following
conditions:

         6.1 REPRESENTATION. The representations and warranties made by the
Purchaser in Section 4 hereof shall be true and correct when made and shall be
true and correct on Closing with the same force and effect as if they had been
made immediately prior to the Closing and as of such time.

        6.2 Purchaser has fulfilled any and all of its obligations set forth in
Section 1.1.

                                   SECTION 6A
                               BOARD OF DIRECTORS

         Subsequent to the Closing, the Board of Directors will consist of six
(6) directors, three of whom will be appointed by Zohar Zisapel, Yehuda Zisapel
and RAD Data Communications Ltd., the fourth will be Amos Amir in his capacity
as Managing Director of the Company, and the fifth and the sixth are entitled to
be appointed by The Trust Company of Maritime Bank of Israel ("Maritime") and
Clal Venture Capital LP ("Clal"). Lannet Data Communications Ltd. and Finovelec,
will have the right to designate one observer each to the Board of Directors.
Upon reasonable notice, Lannet will be permitted to change the status of its
observer to that of director, in which event the number of directors will be
eight (8), Lannet's observer will become the seventh director and Yehuda Zisapel
and Zohar Zisapel will be entitled to appoint another director (the eighth).

                                    SECTION 7
                            COVENANTS OF THE COMPANY

         For as long as the Purchaser's equity interest in the Company will
amount to at least five (5%) percent of the outstanding capital securities
therein and Purchaser has the right to appoint a director or an observer under
Section 6A hereinabove, except where stated otherwise in this Section 7 and in
Section 8, and without derogating from any rights or obligations conferred upon
shareholders, or obligations conferred upon corporations, under applicable law,
the Company hereby covenants and agrees as follows. For the purposes of
calculating Clal's percentage of ownership set forth above, ECI Telecom Ltd.'s
("ECI") equity interest in the Company at the time will be taken into account
and added to that of Clal for as long as Clal is a shareholder of ECI.


                                       7
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         7.1 ADDITIONAL INFORMATION. The Company will permit an employee of the
Purchaser to visit upon a mutually convenient time and inspect any of the
properties of the Company, including its books of account, and to discuss its
affairs, finances and accounts with the Company's officers and the Auditor.

                  (a) As soon as available after approval by the Board of
Directors, the Company will provide Purchaser with a summary of the budget,
including projected yearly profit and loss accounts and balance sheet, as
contained in its Operating Plan and as approved by its Board of Directors, as
well as information about material changes in the budget, all as approved by the
Board of Directors.

                  (b) With reasonable promptness, the Company agrees to provide
to Purchaser such information and data with respect to the Company, as the
Purchaser may from time to time reasonably request.

                  The foregoing provisions of this Section 7.1 shall not be in
limitation of any rights which the Purchaser may have to inspect and copy the
books and records of the Company or to inspect its properties or discuss its
affairs, finances and accounts, under the laws of the State of Israel.

         7.2 USE OF PROCEEDS. The Company will use the proceeds of the issuance
and sale of the Shares mainly to fund its activities and its business subject to
any resolutions made by its Board of Directors from time to time.

         7.3 BOARD APPROVAL. Without derogating from the Company's Articles of
Association, or any law or practice limiting the authority of the management of
the Company, the Company shall ensure that the approval of the Board of
Directors of the Company shall be required for the following, (i) designation of
all authorized signatories; (ii) approval of the Company's or the subsidiaries'
budget and Operating Plan; (iii) selection of legal counsel of the Company; (iv)
terms of employment of the Managing Director of the Company; and (v) any and all
other matters with regard to which the Board of Directors of the Company
resolves that its prior approval shall be required.

         Without derogating from the first sentence of Section 7 hereof, it is
further provided that the Purchaser's rights hereunder shall expire upon a
public offering of the Company's shares regardless of Purchaser's percentage of
ownership at that time.

         7.4 Resolutions of the Board of the Company regarding the following
subject matters shall require the consent of five out of six directors. In the
event that the Board will consist of 8 directors as per Section 6.2 hereinabove,
then the following subject matters will require the consent of 6 out of 8
directors, including consent of two directors out of the following: "Clal"
Director, "Maritime" Director, "Lannet" Director:

                (a) A merger of the Company with any other entity;

                (b) Acquisition or disposition, including mortgage, of other
corporations, real estate, and any material assets out of the ordinary course of
the Company's business;

                (c) Replacement of the Company's Managing Director;


                                       8
<PAGE>

                (d) Replacement of the auditors of the Company;

                (e) Approval of the distribution of dividends by the Company.

                (f) Loans by the Company or any of its subsidiaries to their
directors or officers, or to their relatives or other affiliates, with the
exception of employees receiving shares under the trust as set forth in
subsection 3.23 hereinabove;

                (g) Transactions in excess of $20,000 not included in the
approved Operating Plan between the Company or its affiliates and their
directors, officers and employees or their relatives or other affiliates, with
the exception of employees receiving shares under the trust as set forth in
subsection 3.23 hereinabove;

                (h) All material transactions or obligations not contemplated in
the budget by the Company or its subsidiaries; and

                (i) Resolution to enter a new business field unrelated to the
present field.

         Notwithstanding anything to the contrary contained herein, in the event
that a director is not allowed under a specific section of this Agreement to
participate in a board meeting and/or discussion, the majority required will be
(1) 4 out of 5, or (2) 5 out of 7, including only one of the following: the Clal
Director, Maritime Director, or Lannet Director.

         7.5 RIGHT OF FIRST REFUSAL FOR IPO. The Company agrees that in the
event that the Board of Directors resolves:

                (a) to initially offer shares of the Company on the Israeli
Stock Exchange, then the following will apply:

                        (1) The Company will inform Clal Issuing Ltd. of said
resolution;

                        (2) Clal Issuing Ltd. will have an option for twenty
(20) days as of said notice date by the Company to make a proposal to underwrite
the offering (hereinafter, the "Clal Proposal");

                        (3) The Board of Directors will consider the Clal
Proposal and will, in its sole discretion, resolve whether it is acceptable or
not; and

                        (4) In the event that the Board resolves not to accept
the Clal Proposal, then the Company will be free to negotiate and agree with any
underwriter whatsoever.

                        (5) Within five (5) working days after the written
notice of the Company of the best proposal from the underwriter as in (4) above,
Clal will have the option to improve the Clal Proposal to match the
underwriter's proposal. In the event that Clal Issuing Ltd. either fails to
respond or to match the other proposal, Clal's option under this Section 7.5(a)
will terminate and the Board will be free to proceed as it deems fit.


                                       9
<PAGE>

                  (b) In the event that the Board of Directors resolves to
initially offer shares of the Company on NASDAQ, with some of the shares
intended for the Israeli public, then the following will apply:

                        (1) The Company will inform Clal Issuing Ltd. of said
resolution;

                        (2) The Company will be free to negotiate and agree with
any underwriting house to underwriter the offering, provided that the Company
notifies said underwriter that Clal Issuing Ltd. has a right of first refusal
concerning the offering of the shares of the Company to the Israeli public.

                  (c) In the event that the Board of Directors resolves to
engage a placement agent for a private offering in the Israeli market, and such
agent is entitled to a commission in return for his services (whether by form of
money or options), then the following will apply:

                        (1) The Company will inform Clal Venture Capital LP of
said resolution;

                        (2) Clal Issuing Ltd. will have an option for ten (10)
days as of said notice date by the Company to make a proposal to head the
offering as a placement agent (hereinafter, the "Clal Proposal");

                        (3) Within five (5) working days after the written
notice of the Company of a proposal from another placement agent, Clal and Clal
Issuing Ltd. will have the option to improve the Clal Proposal to match the
other proposal. In the event that Clal Issuing Ltd. either fails to respond or
to match the other proposal, Clal's option under this Section 7.5(c) will
terminate and the Board will be free to proceed as it deems fit;

                        (4) The Board of Directors will consider the Clal
Proposal as well as the other proposal(s) and will, in its sole discretion,
resolve whether it is acceptable or not; and

                        (5) In the event the Board accepts Clal Issuing Ltd.'s
proposal and Clal Issuing Ltd. acts as the said placement agent, then,
notwithstanding anything to the contrary contained herein, the Board, in its
sole discretion, by simple majority, will be free thereafter to resolve that the
services of Clal Issuing Ltd. as a placement agent are not satisfactory, to
terminate such services and to receive such services from any other placement
agent without any further rights or obligations with respect to Clal Issuing
Ltd. or the Purchasers.

                (d) It is specifically agreed that:

                        (1) all discussions concerning the identity of
underwriter or placement agent as well as the terms of the offer under Section
7.5 will be without the presence of Clal's appointed director;

                        (2) Clal Venture Capital LP's and Clal Issuing Ltd.'s
rights under Section 7.5 will terminate upon acceptance or rejection by the
Board of Directors of the Clal Proposal;


                                       10
<PAGE>

                        (3) It is further provided that the rights of Clal
Issuing Ltd., and Clal Venture Capital LP under Section 7.5 shall expire upon a
public offering of the Company's shares regardless of Purchaser's percentage of
ownership at that time.

                        (4) For the purposes of this Agreement, the address of
Clal Issuing Ltd. is 5 Druianov Street, Tel-Aviv 63143.


                                    SECTION 8

         For as long as the Purchaser's equity interest in the Company amounts
to at least two (2%) percent of the outstanding share capital of the Company
therein, and without derogating from any rights conferred upon shareholders, or
obligations conferred upon corporations under applicable law, the Company hereby
covenants and agrees as follows:

         8.1 PRE-EMPTIVE RIGHTS. If the Company should at any time or from time
to time propose to issue and sell New Securities, as defined in subsection
8.1(a), a pro rata portion of such New Securities shall first be offered (as
hereinafter provided) to the shareholders of the Company (each of whom shall
hereinafter be referred to as "offeree"). For purposes of this Section 8.1, the
pro rata portion of each Offeree shall mean a fraction of the New Securities to
be issued, of which the aggregate number of shares which are held by the Offeree
on the date of the Company's written notification referred to in subsection
8.1(b) below (the "Notice Date") shall be the numerator and the aggregate number
of shares held by all the Offerees shall be the denominator. The aforesaid
rights of the Offerees shall be subject to the following provisions:

                  (a) "New Securities" shall mean any capital stock of the
Company, whether or not now authorized, and rights, options or warrants to
purchase capital stock, and securities of any type whatsoever that are, or may
become, convertible into capital stock; provided that the term "New Securities"
shall not include (i) securities purchased under this Agreement; (ii) securities
offered to the public; (iii) securities issued pursuant to the acquisition of
another corporation by the Company by merger, purchase of substantially all the
assets of another corporation or any other reorganization whereby the Company
owns not less than fifty-one percent (51%) of the voting power of such
corporation; (iv) securities issued to employees, consultants or directors of
the Company pursuant to any stock option plan or stock purchase or stock bonus
arrangement approved by the Board of Directors of the Company; or (v) securities
issued pursuant to payment of any dividend or distribution with respect to the
Company's issued and outstanding capital stock.

                  (b) In the event the Company proposes to undertake an issuance
of New Securities, it shall give each Offeree written notice of its intention,
describing the type of New Securities and the price and the terms upon which the
Company proposes to issue the same, and offering its pro rata portion thereof to
such Offerees at such price and on such terms. Each Offeree shall have
twenty-one (21) days from the date of such notice to accept such offer, in whole
or in part, by written notice to the Company, that has to be received by the
Company during the above mentioned 21 days period. All New Securities as to
which such offers have not been accepted in whole or in part by one or more of
the Offerees (of which fact the Company shall give immediate written notice to
all other Offerees), shall be re-offered to each of the Offerees who have
accepted in full the original offer, and each such Offeree shall have the right,


                                       11
<PAGE>

within ten (10) days of the date of such written notice, to purchase the
respective pro rata portions of such new Securities, the same to be computed as
aforesaid but without regard to the shares held by any Offeree which had not
accepted the original offer in full.

                  (c) In the event any Offeree fails to accept such offers, the
Company shall have the right to sell within six (6) months or enter into an
agreement, to sell such New Securities as to which such offers were not
accepted, provided, however, that no such sale be effected at a price or upon
terms more favorable to the purchasers thereof than those specified in the
Company's notice pursuant to Section 8.1(b).

                  (d) Each of Yehuda Zisapel, Zohar Zisapel and RAD Data
Communications Ltd. shall have a right to allocate any unused portion of the New
Securities offered to him to the other.

                  (e) The Purchaser shall have the right to allocate any unused
portion of the New Securities offered to him to its owners or to a company
affiliated to Purchaser, provided that such recipient of shares will join in
this Agreement as if it had become a party to it as of the receipt of shares.

                  (f) Notwithstanding anything to the contrary contained herein,
Amos Amir, so long as he is the Managing Director of the Company, will be
entitled to be an Offeree under this Section 8.1.

                  (g) Each of Lerosh Investments Ltd., Gevahim Investments House
Limited Ltd., Mr. Yoav Chelouche, Permal Emerging Growth V Ltd., Maritime-Julex
Investment Ltd., Mr. Shraga Blazer and Mr. Eli Luz shall have a right to
allocate any unused portion of the New Securities offered to him to the other.

         8.2 REGISTRATION RIGHTS. If the Company should elect to offer any of
its securities to the public, the Purchaser and the Present Shareholders shall
have registration rights as set forth in EXHIBIT "8.2" attached hereto.

         8.3 RESTRICTIONS. Unless otherwise required by applicable law or under
this Agreement, the Company shall not without the approval of at least 75% of
the shareholders:

                  (a) amend or repeal any provision of, or add any provision to,
the Company's Articles of Association;

                  (b) create any new class or classes of securities of the
Company having any preference or priority as to dividends or assets superior to
any such preference or priority of the Ordinary Shares, or reclassify any of its
existing securities into such superior securities; or

                  (c) approve a merger of the Company with any other entity;

                  Without derogating from the first sentence of Section 8, it is
further provided that each shareholder's rights under Section 8 (except for 8.2)
shall expire upon the initial public offering of the Company's shares,
regardless of that shareholder's percentage of ownership at that time.


                                       12
<PAGE>

                                   SECTION 8A

         The Company agrees and undertakes as follows:

        8A.1 BASIC FINANCIAL INFORMATION. The Company will furnish to the
Purchaser the following reports certified, when so required herein, by the
Company's auditors:

        (a) As soon as practicable after the end of each calendar quarter, and
in any event within forty-five (45) days thereafter, a balance sheet and a
profit and loss account and of cash flow (including opening cash, income,
expenses and closing cash) of the Company as of the end of such quarterly
period, and for the current fiscal year to date, prepared in accordance with
generally accepted accounting principles consistently applied and setting forth
in comparative form the figures for the corresponding periods of the previous
fiscal year, subject to changes resulting from year-end audit adjustments, all
in reasonable detail, signed by the principal financial or accounting officer of
the Company. There shall be appended to such materials a report of the
management as to the business of the Company and its activities during the
quarter.

        (b) Not later than forty-five (45) days after the end of each quarter,
sales figures, backlog and new orders for such quarter.

        Without derogating from the first sentence of Section 7, it is further
provided that the Company will not be required to furnish any information under
the provisions of this Section 8A.1 and of Section 8A.2 below subsequent to the
initial public offering.

        8A.2 INSURANCE. The Company shall continue to maintain insurance
policies similar to those described in Section 3.12 above.

        8A.3 ACCOUNTS AND RECORDS. The Company will keep true records and books
of account in which full, true and correct entries will be made of all dealings
or transactions in relation to its business and affairs in accordance with
generally accepted accounting principles applied on a consistent basis.

        8A.4 PROPRIETARY INFORMATION AND NON-COMPETITION AGREEMENTS. The Company
will not employ, or continue to employ, any person who will have access to
confidential information with respect to the Company and its operations unless
such person has executed and delivered the Company's standard Employment
agreement then in force containing proprietary information and non-competition
sections to the satisfaction (as to substance and form) of the Company's
counsel.


                                    SECTION 9
                  RESTRICTIONS ON TRANSFERABILITY OF SECURITIES

        Except as set forth in this Section 9, the Present Shareholders and the
Purchaser agree not to sell or transfer any of their shares and rights in the
Company to a third party. This Section 9 will terminate upon the initial
offering of the Company's shares to the public.

        9.1 For the purpose of this Section 9, the shareholders, the
Purchaser and the Other Purchasers will be regarded as the following Groups:


                                       13
<PAGE>

               (a) Zisapel Group - Yehuda Zisapel, Zohar Zisapel, the Trust and
RAD Data Communications Ltd.

               (b) Clal Group - Clal Venture Capital LP, ECI Telecom Ltd.

               (c) Finovelec Group - Finovelec, Factory Systemes, Houston
Venture Partners Ltd.

               (d) Capital Group - Zohar Gilon, Avraham Neuman, Yair Tauman,
W.S.P. Capital

               (e) Maritime Group - Lerosh Investments Ltd., Gevahim Investments
House Limited Ltd., Mr. Yoav Chelouche, Permal Emerging Growth V Ltd.,
Maritime-Julex Investment Ltd., Mr. Shraga Blazer and Mr. Eli Luz.

         9.2 Group Members are entitled to transfer shares among
themselves for consideration or without consideration without any
restrictions.

         9.3 Except as set forth in sections 9.9, 9.10 and 9.11 hereinbelow,
any shareholder who shall elect to transfer (hereinafter "Seller") all or
part of his shares, not in accordance with subsection  9.2 (hereinafter
"Offered Shares") shall offer them first to the other registered shareholders
of the Company at that time (hereinafter "Offerees") on a pro rata basis
based on their share in the share capital of the Company.

         9.4 In the event any such Offeree fails to exercise his right to
purchase his Offered Shares within forty-five (45) days from the date the
offer is made, then the Seller shall have the right to offer the Offered Shares
to a third party at the same price and upon the same terms of sale as those
offered to the other shareholders under section 9.3 and provided that said
third party shall undertake all of Seller's obligations under this Agreement.
(Such third party to be called hereunder, the "Transferee"). In the event
that the shares are not sold to said party within six (6) months as of the
offer to such said third party, then Section 9.3 will apply anew.

         9.5 The Board of Directors shall have the right to not approve the
transfer of shares to a third party in each of the following events:

                (i) If the third party is a competitor of the Company;

                (ii) If there is a possibility of conflict of interest between
        the third party and the Company;

                (iii) For any other reason, in which case such approval shall
        not be unreasonably withheld.

         9.6 In the event that Yehuda Zisapel and/or Zohar Zisapel and/or RAD
will sell more than a total of 25% of their shares in the Company to third
parties, then Purchaser will have the right to sell the same portion of
Purchaser's shares in the Company under the same terms and conditions
(hereinafter, the "Tag Along Right"). Purchaser will inform Zisapel in writing
by fax and by confirmation by mail if it intends to exercise its Tag Along Right
within ten (10) days


                                       14
<PAGE>

after the date of notice by Zisapel to Purchaser. Failure to respond will be
deemed as a decision not to Tag Along.

        9.7 This Section 9 will supersede Section 14 of the Inception Agreement.

        9.8 The terms of the Trust Agreement, EXHIBIT 3.23, will have priority
over this Section 9.

        9.9 Finovelec, in its discretion, shall be permitted to freely transfer
up to 5% of its shares (at that time) in the Company to up to 6 of Finovelec
executives, as well as up to an additional 5% of its shares (at that time) in
the Company to IDI (if then an affiliate of Finovelec). Such transfer shall be
considered a transfer among the Finovelec Group, provided that each Transferee,
upon receipt of the shares, will join this Agreement and undertake all of
Finovelec's obligations hereunder and will be considered henceforth a member in
the Finovelec Group for the purpose of this Section 9.

        9.10 Clal Venture Capital LP is entitled to transfer all of its shares
in the Company to its partners, provided that each Transferee, upon receipt of
the shares, will join this Agreement and undertake all of Purchaser's
obligations hereunder and will be considered henceforth a member in the Clal
Group for the purpose of this Section 9.

        9.11 Each of Zohar Gilon, Avraham Neuman and Yair Tauman is entitled,
once, to transfer his shares to a company directly under the total control of
said person, provided that each Transferee, upon receipt of the shares, will
join this Agreement and undertake all of Purchaser's obligations hereunder and
will be considered henceforth a member in the Capital Group for the purpose of
this Section 9.

                                   SECTION 9A
                                  ANTI-DILUTION

        (a) In the event that any time prior to the earlier of the Closing of
the Company's initial public offering or three (3) years from the date of this
Agreement, the Company issues or sells any Ordinary Shares to third parties upon
a private placement (excluding Company employees) for consideration per share of
less than US $135 (an "Offering"), then prior to said private placement the
Purchaser shall be given the option to purchase Ordinary Shares of the Company
at par value (NIS 1.- per share), in an amount computed as set forth below.

        (b) The amount of shares to be issued to Purchaser will be computed
according to the following table:

------------------------------------- ------------------------------------------
SHARE PRICE AT NEXT PRIVATE PLACEMENT ADDITIONAL SHARES ISSUED TO ALL PURCHASERS
                                        (DISTRIBUTED ON A PRO-RATA BASIS)
------------------------------------- ------------------------------------------
          $134.99 to $101.01                          7,489*
------------------------------------- ------------------------------------------
          $101.00 to $50.51                          17,959*
------------------------------------- ------------------------------------------
           Less than $50.5                           33,642*
------------------------------------- ------------------------------------------

*    The number and price of shares will be adjusted in the event of any
restructuring of the Company's share capital.


                                       15
<PAGE>

        (c) Upon the occurrence of each event giving rise to a right pursuant to
this Section, the Company will, at its expense, promptly compute the number of
Ordinary Shares that each Purchaser is entitled to purchase in accordance with
the terms hereof, and furnish to the Purchaser, a notice of such right and the
number of shares Purchaser is entitled to.

        (d) Any and all of Purchaser's rights under this Section 9A will
terminate within the earliest of: (i) the Closing of the Company's initial
public offering or (ii) three (3) years from the date of this Agreement or (iii)
upon the first private placement contemplated after the Closing set forth in
Section 9A hereinabove.


                                   SECTION 10
                                  MISCELLANEOUS

         10.1 ARBITRATION. All disputes arising under this Agreement or in
connection with the transactions hereunder shall be resolved between the parties
in good faith; however, if these efforts fail, the dispute shall be resolved by
arbitration by a sole arbitrator within sixty (60) days. The arbitrator shall be
chosen by agreement of the parties hereto. If they fail to so agree within
twenty (20) days after a party shall have requested such arbitration, the
arbitrator shall be appointed by the Chairman of the Israeli Bar who shall also
determine the place of the arbitration proceedings based on the convenience of
the parties involved; provided, however, that the arbitrator chosen shall be
from the jurisdiction chosen by the above-mentioned Chairman. The arbitrator
shall not be bound by any judicial rules of evidence or procedure. The arbitral
award shall be final and binding upon the parties, and judgment upon the award
may be entered in any court having jurisdiction, or application may be made to
such court for a judicial acceptance of the award or for an order of
enforcement, as the case may be. The provisions of this Section 10.1 shall apply
to all disputes arising in connection with this Agreement. Each party shall bear
its own expenses, subject to the arbitration judgment on the issue of expenses.

         10.2 SURVIVAL. The representations, warranties, covenants and
agreements made herein shall survive (i) any investigation made by the Purchaser
and (ii) the Closing.

         10.3 SUCCESSORS AND ASSIGNS. Except as otherwise expressly provided
herein, the provisions hereof shall inure to the benefit of, and be binding
upon, the successors, assigns, heirs, executors and administrators of the
parties hereto; provided, however, that no party may assign its rights hereunder
without the prior written consent of the other parties hereto.

         10.4 ENTIRE AGREEMENT; AMENDMENT. This Agreement (including the
Schedules and Exhibits hereto) and the other documents delivered pursuant hereto
constitute the full and entire understanding and agreement between the parties
with regard to the subject matters hereof and thereof and supersede all prior
agreements and understandings relating thereto. Neither this Agreement nor any
term hereof may be amended, waived, discharged or terminated except by an
instrument in writing signed by all the parties hereto.

         10.5 NOTICES. All notices and other communications required or
permitted to be given or sent hereunder shall be in writing and shall be deemed
to have been sufficiently given or delivered for all purposes if mailed by
registered airmail, transmitted by telex or telecopier, or


                                       16
<PAGE>

delivered by hand to the following respective addresses until otherwise directed
by notice as aforesaid:

                                  To the Purchaser:

                                  RAD Data Communications Ltd.
                                  12 Hanechoshet Street
                                  Tel Aviv 69710, Israel

                                  Attention:  Mr. Zohar Zisapel

                                  To the Company:

                                  RADVISION Ltd.
                                  8 Hanechoshet Street
                                  Tel Aviv 69710, Israel

                                  Attention:  Mr. Amos Amir

provided, however, that notice of change of address shall be effective only upon
actual receipt.

                  All notices sent by registered mail shall be deemed to have
been received within seventy-two (72) hours of posting. If delivered by hand,
upon their delivery.

         10.6 DELAYS OR OMISSIONS. No delay or omission to exercise any right,
power or remedy upon any breach or default under this Agreement shall impair any
such right, power or remedy of such holder nor shall it be construed to be a
waiver of any such breach or default, or in acquiescence therein, or of any
similar breach or default thereafter occurring; nor shall any waiver of any
single breach or default be deemed a waiver of any other breach or default
theretofore or thereafter occurring. Any waiver, permit, consent or approval of
any kind or character on the part of any holder of any breach or default under
this Agreement, or any waiver on the part of any holder of any holder of any
provisions or conditions of this Agreement shall be effective only if made in
writing and only to the extent specifically set forth in such writing. All
remedies, either under this Agreement or by virtue of law or otherwise afforded
to any holder, shall be cumulative and not alternative.

         10.7 WAIVER OF DEFAULT. No waiver with respect to any breach or default
in the performance of any obligation under the terms of this Agreement shall be
deemed to be a waiver with respect to any subsequent breach or default, whether
of similar or different nature.

         10.8 RIGHTS; SEVERABILITY. In case any provision of the Agreement shall
be invalid, illegal or unenforceable, the validity, legality and enforceability
of the remaining provisions shall not in any way be affected or impaired
thereby. The parties hereto shall be obliged to draw up an arrangement in
accordance with the meaning and the object of the invalid provision.

         10.9 CONFIDENTIAL INFORMATION. The Purchaser acknowledges that the
information received by it and such information which will be received pursuant
hereto shall be confidential and is intended for the Purchaser's use only for
the purpose of this Agreement, and the Purchaser will not use or allow the use
of such confidential information or reproduce, disclose or


                                       17
<PAGE>

disseminate such information to any other person (other than the Purchaser's
employees or agents having a need to know the contents of such information, and
the Purchaser's attorneys), except in connection with the exercise of rights
under this Agreement, unless the Company has made such information available to
the public generally or the Purchaser is required to disclose such information
by a governmental body or by judicial order, but only to the persons and the
extent so required.

        10.10 TITLES AND SUBTITLES. The titles of the sections and subsections
of this Agreement are for convenience of reference only and are not to be
considered in construing this Agreement.

        10.11 GOVERNING LAW. This Agreement shall be governed exclusively by,
and construed solely in accordance with, the laws of the State of Israel.

        10.12 (DELETED)

        10.13 Purchaser agrees that the Company will issue to Mr. Eliezer Manor
forty-nine (49) shares against payment of their nominal value.

        10.14 Following the Closing, the Company will amend its Memorandum and
Articles of Association to reflect this Agreement. The Present shareholders and
the Purchasers agree to such amendments.

        10.15 The Company will bear the cost of stamp tax due in connection with
the issuance of shares according to this Agreement.

        IN WITNESS WHEREOF, the parties hereto have executed this Agreement in
three (3) original copies, one to the Company, one to the Purchaser and one of
the Present Shareholders, as of the date first above-mentioned.

THE COMPANY                                 THE PURCHASER
RADVISION LTD.                              RAD DATA COMMUNICATIONS LTD.


By: /s/  AMOS AMIR                          By: /s/ ZOHAR ZISAPEL
    ----------------------------                ----------------------------
    Amos Amir, Managing Director            Zohar Zisapel, Managing Director


THE PRESENT SHAREHOLDERS:


/s/ YEHUDA ZISAPEL                          /s/ ZOHAR ZISAPEL
--------------------------------            --------------------------------
Yehuda Zisapel                              Zohar Zisapel


<PAGE>

                                    EXHIBIT 1

<TABLE>
<CAPTION>
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
                                           NO. OF SHARES                     SHARES       TOTAL NO.      OWNERSHIP
                                           PRIOR TO          INVESTED        ISSUED AT    AFTER CLOSING  AFTER
NAME OF SHAREHOLDER                        INVESTMENT        AMOUNT          CLOSING                     CLOSING
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
<S>                                        <C>               <C>             <C>          <C>            <C>
Yehunda Zisapel                                       6,930                                       6,930       15.34%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Zohar Zisapel                                         6,930                                       6,930       15.34%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Yehuda Zisapel and Zohar Zisapel (as                  5,940                                       5,940       13.15%
trustees)
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Amos Amir                                               932                                         932        2.06%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
RAD Data Communications Ltd.                                        710,030                       3,515        7.78%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Zohar Gilon                                                          60,600                         300         .66%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Avraham Neuman                                                       60,600                         300         .66%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Yair Tauman                                                          60,600                         300         .66%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
W.S.P. Capital Investments Ltd.                                      37,976                         188         .42%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Lannet Data Communications Ltd.                                     999,900                       4,950       10.95%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Lerosh Investments Ltd.                                              99,990                         495        1.10%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Gevahim Investments House Limited Ltd.                               20,200                         100         .22%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Yoav Chelouche                                                       49,692                         246        0.54%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Permal Emerging Growth V Ltd.                                       194,930                         965        2.14%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Maritime-Julex Investment Ltd.                                       99,990                         495        1.10%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Shraga Blazer                                                         5,050                          25        0.06%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Eli Luz                                                              30,098                         149        0.33%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Clal Venture Capital LP                                             999,900                       4,950       10.95%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
ECI Telecom Ltd.                                                    499,950                       2,475        5.48%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Eliezer Manor                                                                                        49        0.11%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Finovelec                                                           550,046                       2,723        6.03%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Factory Systemes                                                    250,076                       1,238        2.74%
------------------------------------------ ----------------- --------------- ------------ -------------- ------------
Houston Venture Partners Ltd.                                       199,980                         990        2.19%
------------------------------------------ ================= =============== ============ ============== ============
                                                     20,732       4,929,608                      45,185      100.00%
------------------------------------------ ================= =============== ============ ============== ============
</TABLE>


<PAGE>

                                   EXHIBIT 5.7



To:      Purchaser
         (as defined in the attached Agreement
         dated April 18, 1995)

                                     OPINION

I, the undersigned, as counsel to RADVision Ltd., hereby give my opinion, to the
best of my knowledge at this time as follows:

         1. ORGANIZATION AND STANDING. RADVision Ltd. ("RADVision") is a company
duly organized and existing under the laws of the State of Israel and is in good
standing under such laws. RADVision has the requisite corporate power to own and
operate its properties and assets and to carry on its business as presently
conducted.

         2. CAPITALIZATION. The RADVision' s authorized capital is sixty
thousand (60,000) Ordinary Shares. The RADVision's issued capital stock
immediately prior to the Closing date shall consist of twenty thousand seven
hundred thirty-two (20,732) Ordinary Shares, all of which are duly authorized,
validly issued and free of any liens or encumbrances. Out of the issued share
capital, thirteen thousand eight hundred sixty (13,860) shares are fully paid
and six thousand eight hundred seventy-two (6,872) shares are partially paid.
All shares are non-assessable, and to the best of RADVision `s knowledge and
belief, are beneficially owned by their holders of record. There are no
preemptive, conversion or other rights, options, or agreements granted or issued
by, or binding upon, RADVision or the shareholders which entitle any person,
firm or corporation to purchase or acquire any shares of RADVision's capital
stock, except as set forth in this Agreement.

         The rights, restrictions, privileges and preferences with respect to
RADVision's shares, as set forth in its Memorandum of Association and Articles
of Association, are valid and enforceable. To the best of my knowledge, there
are no outstanding rights, options, warrants, conversion rights or agreements
for the purchase or acquisition from RADVision of any shares of its capital
stock, except as stated in its Memorandum and Articles of Association.

         3. COMPLIANCE WITH LAW AND OTHER INSTRUMENTS. The execution, delivery
and performance of the Agreement dated April 18, 1995 between RADVision and the
Purchaser (the "Agreement") will not result in any violation of, or be in
conflict with or constitute a default under, any applicable law, regulation or
order, RADVision's Memorandum of Association or Articles of Association. To the
best of my knowledge, the execution, delivery and performance of the Agreement
and consummation of the transactions contemplated thereby, will not result in
any violation of, or be in conflict with or constitute a default under, any term
of any mortgage, indenture, contract, agreement, instrument, judgment, decree or
order applicable to RADVision, or result in the creation of any mortgage,
pledge, lien, encumbrance or charge upon any of the properties or assets of
RADVision pursuant to any such term.


<PAGE>

         4. LITIGATION. To the best of my knowledge, there are neither any
actions, proceedings nor investigations pending or threatened against RADVision
or its assets or properties.

         5. EMPLOYMENT AGREEMENTS. The agreements between RADVision and its
employees (except for Danny Levin) as referred to in Sections 5.5 and 5.6 of the
Agreement have been duly executed and delivered by, and constitute valid and
binding obligations of, all such employees, enforceable by RADVision in
accordance with their terms.

         6. STATEMENTS AND FACTS. Nothing has come to my attention that would
lead me to believe that the Agreement contains any untrue statement of a
material fact or omits to state a material fact necessary to make the statements
therein not misleading.


                                           /s/ NEHAMA SNEH
                                           ------------------------------
                                           Nehama Sneh
                                           Advocate



Dated:  April 18, 1995


(opinion/6)


<PAGE>

                                   EXHIBIT 8.2

                               REGISTRATION RIGHTS

         1. INCIDENTAL REGISTRATION. If the Company shall elect to offer any of
its securities to the public, it shall give notice to the Purchaser of such
intention and shall include in such offering a portion of all shareholders
shares equal to the total amount of shares registered, multiplied by an amount
derived by dividing the number of Shares held by each shareholder by the total
number of shares outstanding at that time. In the event the public offering
involves an underwriting, the rights of the shareholders hereunder shall be
conditional upon the underwriter's determination as to marketing factors
requiring the limitation of such right, and the underwriter may preclude from
the offering any or all securities which could have otherwise been included in
the offering.

         2. DEMAND REGISTRATION. At any time commencing one year following the
closing of the Company's initial public offering, and for a period of three (3)
years thereafter, each group of shareholders as defined in section 9.1 and/or
Lannet Data Communications Ltd. shall be entitled to demand one registration of
any or all of its shares held at the time of the initial public offering for
trading on any securities exchange; PROVIDED, however, that such request must
cover Shares representing a market value at the time of such request equal to a
minimum of three million Dollars ($3,000,000); and PROVIDED FURTHER, however,
that such request may not include Shares which within three months from the date
of such request could be sold to the public without restriction, for example
pursuant to the provisions of Rule 144 of the Securities and Exchange
Commission. Within 20 days after receipt, the Company shall give written notice
of such request to the other shareholders and shall include in such registration
all Shares held by them with respect to which the Company receives written
requests for inclusion therein within 15 days after the receipt of the Company's
notice. Thereupon, the Company shall use its best efforts to effect the
registration as soon as possible of all Shares (as to which it has received
requests for registration) for trading on a securities exchange, where the
Shares are then traded, specified in the request for registration. In the event
the registration involves an underwriting, the rights of the shareholders
hereunder shall be conditional upon the underwriter's determination as to
marketing factors requiring the limitation of such right, and the underwriter
may preclude from the offering any or all securities which could have otherwise
been included in the offering. Notwithstanding any other provision of this
clause 2 of Exhibit 8.2, after the Company has effected one such registrations
pursuant to this clause 2, and such registrations have been declared or ordered
effective, in the event that the Company shall furnish to such shareholder(s)
delivering a request for registration a certificate signed by the President 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 or its shareholders
for a registration statement to be filed in the near future, the Company's
obligation to use its best efforts to register, qualify or comply under this
clause 2 shall be deferred for a period not to exceed 120 days from the date of
receipt of such request.

         3. EXPENSES. All expenses incurred in connection with a registration
under Section 2 shall be borne by the selling shareholders participating in such
registration on a pro rata basis; PROVIDED, however, that the Company shall pay
any expenses associated with such registration which the Company would have
incurred in the ordinary course of business. All


<PAGE>

expenses incurred in connection with a registration under Section 1 shall be
borne by the Company; PROVIDED, however, that each of the shareholders
participating in such registration shall pay its pro rata portion of the fees,
discounts or commissions payable to any underwriter.