Document:

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                                                                    EXHIBIT 4.5

                       RESTRICTED STOCK PURCHASE AGREEMENT

        This Agreement is made as of the 1st day of July, 1996, by and between
SkyStream Corporation, a California corporation (the "Corporation"), and _____
________ ("Purchaser").

        In consideration of the mutual covenants and representations herein set
forth, the Corporation and Purchaser agree as follows:

        1. PURCHASE AND SALE OF STOCK.

           (a) Subject to the terms and conditions of this Agreement, the
Corporation hereby agrees to sell to Purchaser and Purchaser agrees to purchase
from the Corporation on the Closing Date (as herein defined), 1,000,000 shares
of the Corporation's Common Stock (the "Stock") at a price of $.01 per share,
for an aggregate purchase price of $10,000. The purchase price for the Stock
shall be paid in cash as full payment for all of the shares.

        2. CLOSING. The purchase and sale of the Stock shall occur at a Closing
to be held at such time and place (the "Closing Date"), as designated by the
Corporation by written notice of at least two business days. The Closing will
take place at the principal office of the Corporation or at such other place as
shall be designated by the Corporation. At the Closing, Purchaser shall deliver
to the Corporation a check payable to the order of the Corporation in the
aggregate amount of the purchase price of the Stock, and the Corporation will
issue, as promptly thereafter as practicable, a certificate representing the
Stock registered in the name of Purchaser.

        3. PURCHASE OPTION.

           (a) All of the Stock shall be subject to the right and option of the
Corporation to repurchase the Stock ("Purchase Option") as set forth in this
paragraph 3. In the event Purchaser shall cease to be employed by the
Corporation (including a parent or subsidiary of the Corporation) for any reason
or no reason, with or without cause, including disability, death, retirement or
other involuntary termination (a "Termination"), the Purchase Option shall come
into effect. Following a Termination, the Corporation shall have the right, as
provided in Section 4 below, to purchase from the Purchaser or the estate of
Purchaser, as the case may be, at the per share price per share originally paid
as set forth in paragraph 1 hereof (the "Option Price"), a portion of the Stock
as follows:

               (i) If the Termination occurs before July 1, 1997, the Purchase
Option shall apply to 100% of the Stock.

               (ii) If the Termination occurs after July 1, 1997, the Purchase
Option shall apply to that portion of the Stock which is a fraction of 100% of
the Stock, the numerator of which shall be

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a number equal to 48 minus the total number of calendar months of the
Purchaser's Vested Service (as defined below) for the Corporation and the
denominator of which shall be 48. "Vested Service" by the Purchaser for the
Corporation shall be defined as that period of time during which the Purchaser
is employed by the Corporation after July 1, 1996 (the vesting commencement
date) excluding time periods during which Purchaser is on an unpaid leave of
absence from such employment.

           (b) Within thirty (30) days following a Termination, the Corporation
shall notify Purchaser by written notice delivered or mailed as provided in
subparagraph 13(c), as to whether it wishes to purchase the Stock pursuant to
exercise of the Purchase Option. If the Corporation elects to purchase the Stock
hereunder, it shall set a date for the closing of the transaction at a place
specified by the Corporation no later than ten (10) days from the date of such
notice. At the closing, the Corporation shall tender payment for the Stock and
the certificates representing the Stock so purchased shall be canceled.
Purchaser hereby authorizes and directs the Secretary or Transfer Agent of the
Corporation to transfer the Stock as to which the Purchase Option has been
exercised from Purchaser to the Corporation. The Option Price may be payable, at
the option of the Corporation, in cancellation of all or a portion of any
outstanding indebtedness of Purchaser to the Corporation or in cash, as set
forth below.

           (c) Nothing in this Agreement shall affect in any manner whatsoever
the right or power of the Corporation, or a parent or subsidiary of the
Corporation, to terminate Purchaser's employment, for any reason, with or
without cause.

        4. LEGALITY OF CORPORATE DISTRIBUTIONS. Notwithstanding any other
provision in this Agreement, the Corporation shall not be required to purchase
or pay for any Stock purchasable or purchased by it hereunder, if such purchase
or such payment of all or any part of the purchase price shall be or constitute,
in the good faith determination of the President or Board of Directors of the
Corporation, an unlawful corporate distribution in contravention of the laws of
any state having jurisdiction with respect to the transactions contemplated
hereby. In the event of such determination and due notice thereof to Purchaser,
any transferee of the Stock or their respective estates, as the case may be,
each date of making any such purchase or making any such payment hereunder by
the Corporation, respectively, may be extended from time to time at the option
of the Corporation for up to two (2) years. If any such purchase is not made and
fully paid for within three (3) years after such purchase was to have been made
pursuant to the terms of this Agreement, however, Purchaser or any transferee of
the Stock or their respective estates, as the case may be, shall have the option
to have the transaction rescinded.

        5. STOCK SPLITS, ETC. If, from time to time during the term of this
Agreement:

           (a) There is any stock dividend or liquidating dividend of cash
and/or property, stock split or other change in the character or amount of any
of the outstanding securities of the Corporation; or

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           (b) There is any consolidation, merger or sale of all, or
substantially all, of the assets of the Corporation;

               then, in such event, any and all new, substituted or additional
securities or other property to which Purchaser is entitled by reason of
Purchaser's ownership of Stock shall be immediately subject to this Agreement
and be included in the word "Stock" for all purposes with the same force and
effect as the shares of Stock presently subject to the terms of this Agreement.

        6. RESTRICTION ON TRANSFER. Purchaser shall not sell, transfer, pledge,
hypothecate or otherwise dispose of any shares of the Stock except in accordance
with the terms of this Agreement. Unless prior written consent is obtained from
the Corporation, any transfer, sale, assignment, hypothecation, pledge,
encumbrance, alienation, or other disposition of any of the Stock, or any
interest therein other than according to the terms of this Agreement, shall be
void and shall transfer no right, title, or interest in or to any or all of the
Stock to the purported transferee, buyer, assignee, pledgee, or encumbrance
holder. Notwithstanding any provision of this Agreement to the contrary, under
no circumstances shall any sale or other transfer or disposition of Stock
subject to this Agreement or any interest therein be valid if such sale,
transfer or disposition of Stock will, or could, impair the ability of the
Corporation to be treated as an S corporation under Section 1361 of the Internal
Revenue Code of 1986, as amended (or any successor statute of the same or
similar effect applicable to the Corporation).

               The Corporation shall not be required (i) to transfer on its
books any shares of Stock which shall have been disposed of in violation of any
of the provisions set forth in this Agreement, or (ii) to treat as owner of such
shares or to accord the right to vote as such owner or to pay dividends to any
transferee to whom such shares shall have been so transferred.

        7. TERMINATION OF AGREEMENT. The provisions of this Agreement shall
terminate on (i) the closing date of an underwritten public offering of Common
Stock of the Corporation (the "IPO") or (ii) the closing date of a sale of
substantially all of the assets of the Corporation, purchase of substantially
all of the outstanding shares of the Corporation or merger of the Corporation
pursuant to which shareholders of this Corporation receive cash and/or
securities of a buyer whose shares are publicly traded (the "Acquisition").

        8. LEGENDS. All certificates representing the shares of Stock of the
Corporation subject to the provisions of this Agreement shall have endorsed
thereon the following legends:

           (a) "THESE SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES
ACT OF 1933. THEY MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED OR HYPOTHECATED IN
THE ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT AS TO THE SECURITIES UNDER
SAID ACT OR AN OPINION OF COUNSEL SATISFACTORY TO THE CORPORATION THAT SUCH
REGISTRATION IS NOT REQUIRED."

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           (b) "THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RIGHTS
OF FIRST REFUSAL CONTAINED IN THE BYLAWS OF THIS CORPORATION AND IN AN AGREEMENT
BETWEEN THE CORPORATION AND THE REGISTERED HOLDER, COPIES OF WHICH MAY BE
OBTAINED FROM THE SECRETARY OF THE CORPORATION."

           (c) "THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO
CERTAIN RESTRICTIONS UPON TRANSFER AS SET FORTH IN AN AGREEMENT BETWEEN THE
CORPORATION AND THE REGISTERED HOLDER, A COPY OF WHICH IS ON FILE AT THE
PRINCIPAL OFFICE OF THE CORPORATION."

           (d) "THE SECURITIES REPRESENTED HEREBY MAY BE SUBJECT TO RESTRICTIONS
ON TRANSFER FOR A PERIOD OF NOT MORE THAN 180 DAYS FOLLOWING THE EFFECTIVE DATE
OF A REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933, AS AMENDED, FOR AN
OFFERING OF THE CORPORATION'S SECURITIES PURSUANT TO THE TERMS SET FORTH IN AN
AGREEMENT BETWEEN THE CORPORATION AND THE REGISTERED HOLDER, A COPY OF WHICH IS
ON FILE AT THE PRINCIPAL OFFICE OF THE CORPORATION."

           (e) Any legend required to be placed thereon by the California
Commissioner of Corporations or under other applicable state Blue Sky laws.

        9. MARKET STANDOFF. Purchaser hereby agrees that Purchaser shall not, to
the extent requested by the Corporation and an underwriter of common stock (or
other securities) of the Corporation, offer, sell, contract to sell or grant any
option to purchase or otherwise dispose of any of the Stock during a period not
to exceed one hundred eighty (180) days following the effective date of a
registration statement of the Corporation filed under the Securities Act;
provided, however, that such agreement shall be applicable only to the first two
(2) such registration statements of the Corporation which cover shares (or other
securities) to be sold on behalf of the Corporation to the public in an
underwritten public offering.

        In order to enforce the foregoing covenant, the Corporation may impose
stop-transfer instructions with respect to the Stock of Purchaser (and the
shares or securities of every other person subject to the foregoing restriction)
until the end of such period.

        10. PURCHASER'S REPRESENTATIONS. In connection with the purchase of the
Stock, Purchaser hereby represents and warrants to the Corporation as follows:

            (a) INVESTMENT INTENT; CAPACITY TO PROTECT INTERESTS. Purchaser is
purchasing the Stock solely for Purchaser's own account for investment and not
with a view to or for sale in connection with any distribution of the Stock or
any portion thereof and not with any present intention of selling,

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offering to sell or otherwise disposing of or distributing the Stock or any
portion thereof in any transaction other than a transaction exempt from
registration under the Securities Act. Purchaser also represents that the entire
legal and beneficial interest of the Stock is being purchased, and will be held,
for Purchaser's account only, and neither in whole or in part for any other
person. Purchaser either has a pre-existing business or personal relationship
with the Corporation (including a parent, affiliate or subsidiary of the
Corporation) or any of its officers, directors or controlling persons or by
reason of Purchaser's business or financial experience or the business or
financial experience of Purchaser's professional advisors who are unaffiliated
with and who are not compensated by the Corporation (including a parent,
affiliate or subsidiary of the Corporation) or any affiliate or selling agent of
the Corporation, directly or indirectly, could be reasonably assumed to have the
capacity to evaluate the merits and risks of an investment in the Corporation
and to protect Purchaser's own interests in connection with this transaction.

           (b) RESIDENCE. Purchaser's principal residence is located at the
address indicated beneath Purchaser's signature below.

           (c) INFORMATION CONCERNING CORPORATION. Purchaser has heretofore
discussed the Corporation and its plans, operations and financial position with
the Corporation's officers and has heretofore received all such information as
Purchaser has deemed necessary and appropriate to enable Purchaser to evaluate
the financial risk inherent in making an investment in the Stock, and Purchaser
has received satisfactory and complete information concerning the business and
financial condition of the Corporation in response to all inquiries in respect
thereof.

           (d) ECONOMIC RISK. Purchaser realizes that the purchase of the Stock
will be a highly speculative investment and involves a high degree of risk, and
Purchaser is able, without significantly impairing Purchaser's financial
position, to hold the Stock for an indefinite period of time and to suffer a
complete loss on Purchaser's investment.

           (e) RESTRICTED SECURITIES. Purchaser understands and acknowledges
that:

               (i) the sale of the Stock has not been registered under the
Securities Act, and the Stock must be held indefinitely unless subsequently
registered under the Securities Act or an exemption from such registration is
available and the Corporation is under no obligation to register the Stock;

               (ii) the share certificate representing the Stock will be stamped
with the legends specified in Section 8 hereof; and

               (iii) the Corporation will make a notation in its records of the
aforementioned restrictions on transfer and legends.

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           (f) DISPOSITION UNDER RULES 144 AND 701. Purchaser understands that
the shares of Stock are restricted securities within the meaning of Rule 144
promulgated under the Securities Act; that the exemption from registration under
Rule 144 will not be available in any event for at least two years from the date
of purchase and payment (the "Holding Period") of the Stock, and even then will
not be available unless (i) a public trading market then exists for the Common
Stock of the Corporation, (ii) adequate information concerning the Corporation
is then available to the public, and (iii) other terms and conditions of Rule
144 are complied with; and that any sale of the Stock may be made only in
limited amounts in accordance with such terms and conditions.

               Purchaser understands that the resale provisions of Rule 701, if
available, will not apply until 90 days after the Corporation becomes subject to
the reporting obligation under the Securities Exchange Act of 1934 (the
"Exchange Act"). There can be no assurance that the requirements of Rule 144 or
Rule 701 will be met, or that the Stock will ever be saleable.

           (g) FURTHER LIMITATIONS ON DISPOSITION. Without in any way limiting
Purchaser's representations set forth above, or the restrictions set forth in
Section 6 and elsewhere herein, Purchaser further agrees that Purchaser shall in
no event make any disposition of all or any portion of the Stock unless and
until:

               (A) There is then in effect a Registration Statement under the
Securities Act covering such proposed disposition and such disposition is made
in accordance with said Registration Statement; or, (B)(1) Purchaser shall have
notified the Corporation of the proposed disposition and shall have furnished
the Corporation with a detailed statement of the circumstances surrounding the
proposed disposition, (2) Purchaser shall have furnished the Corporation with an
opinion of Purchaser's counsel to the effect that such disposition will not
require registration of such shares under the Securities Act, and (3) such
opinion of Purchaser's counsel shall have been concurred in by counsel for the
Corporation and the Corporation shall have advised Purchaser of such
concurrence.

           (h) VALUATION OF COMMON STOCK. Purchaser understands that the Stock
has been valued by the Board of Directors and that the Corporation believes this
valuation represents a fair attempt at reaching an accurate appraisal of its
worth; Purchaser understands, however, that the Corporation can give no
assurances that such price is in fact the fair market value of the Stock and
that it is possible that, with the benefit of hindsight, the Internal Revenue
Service could successfully assert that the value of the common stock on the date
of purchase is substantially greater than so determined.

               If the Internal Revenue Service were to succeed in a tax
determination that the Stock received had value greater than that upon which the
transaction was based, the additional value would constitute ordinary income as
of the date of its receipt. The additional taxes (and interest) due would be
payable by Purchaser, and there is no provision for the Corporation to reimburse
Purchaser for that tax liability, and Purchaser assumes all responsibility for
such potential tax liability. Under current law, in the event such additional
value would represent more than 25 percent of Purchaser's gross

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income for the year in which the value of the shares were taxable, the Internal
Revenue Service would have six years from the due date for filing the return (or
the actual filing date of the return if filed thereafter) within which to assess
Purchaser the additional tax and interest which would then be due.

               The Corporation would have the benefit, in any such transaction,
if a determination was made prior to the three year statute of limitations
period affecting the Corporation, of an increase in its deduction for
compensation paid, which would offset its operating profits, or, if not
profitable, would create net operating loss carry forward arising from
operations in that year.

           (i) SECTION 83(b) ELECTION. Purchaser understands that Section 83 of
the Internal Revenue Code of 1986, as amended (the "Code") taxes as ordinary
income the difference between the amount paid for the Stock and the fair market
value of the Stock as of the date any restrictions on the Stock lapse. In this
context, "restriction" means the right of the Corporation to buy back the stock
pursuant to this Agreement (the "Purchase Option"). In the event the
Corporation has registered under the Exchange Act, "restriction" with respect to
officers, directors and 10% shareholders also means the six (6) month period
after the Closing during which such officers, directors and 10% shareholders are
subject to suit under Section 16(b) of the Exchange Act. Purchaser understands
that he may elect to be taxed at the time the Stock is purchased rather than
when and as the Purchase Option or six (6) month Section 16(b) period expires by
filing an election under Section 83(b) of the Code with the I.R.S. within thirty
(30) days from the date of purchase. Even if the fair market value of the Stock
equals the amount paid for the Stock, the election must be made to avoid adverse
tax consequences in the future. The form for making this election is attached as
Exhibit 1 hereto. Purchaser understands that failure to make this filing timely
will result in the recognition of ordinary income by Purchaser, as the Purchase
Option lapses, or after the lapse of the six (6) month Section 16(b) period, on
the difference between the purchase price and the fair market value of the Stock
at the time such restrictions lapse.

        PURCHASER ACKNOWLEDGES THAT IT IS PURCHASER'S SOLE RESPONSIBILITY AND
NOT THE CORPORATION'S TO FILE TIMELY THE ELECTION UNDER SECTION 83(B), EVEN IF
PURCHASER REQUESTS THE CORPORATION OR ITS REPRESENTATIVES TO MAKE THIS FILING ON
PURCHASER'S BEHALF.

        11. ESCROW. As security for the faithful performance of the terms of
this Agreement and the Note and to ensure the availability for delivery of the
Stock upon exercise of the Corporation's option to purchase the Stock as set
forth in Section 3 hereof, the Purchaser agrees to deliver to and deposit with
the Secretary of the Corporation, or such other person designated by the
Corporation, as escrow agent in this transaction ("Escrow Agent"), two Stock
Assignments duly endorsed (with date and number of shares blank) in the form
attached hereto as Exhibit 2, together with the certificate or certificates
evidencing the Stock (the "Collateral"); said documents are to be held by the
Escrow Agent and delivered by said Escrow Agent pursuant to the Joint Escrow
Instructions of the Corporation and the Purchaser set forth in Exhibit 3
attached hereto and incorporated by this reference, which instructions shall
also be delivered to the Escrow Agent at the closing hereunder.

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        12. MISCELLANEOUS.

            (a) Subject to the provisions and limitations hereof, Purchaser may,
during the term of this Agreement, exercise all rights and privileges of a
stockholder of the Corporation with respect to the Stock.

            (b) The parties agree to execute such further instruments and to
take such further action as may reasonably be necessary to carry out the intent
of this Agreement.

            (c) Any notice required or permitted hereunder shall be given in
writing and shall be deemed effectively given upon personal delivery or upon
deposit in the United States Post Office, by registered or certified mail with
postage and fees prepaid, addressed to Purchaser at the address shown on the
Corporation's employment records and to the Corporation at the address of its
principal corporate offices (attention: President) or at such other address as
such party may designate by ten (10) days' advance written notice to the other
party hereto.

            (d) Purchaser hereby authorizes and directs the Secretary or
Transfer Agent of the Corporation to transfer the Stock as to which the option
to buy pursuant to Section 3 has been exercised from Purchaser to the
Corporation.

            (e) Nothing in this Agreement shall affect in any manner whatsoever
the right or power of the Corporation, or a parent or subsidiary of the
Corporation, to terminate Purchaser's employment, for any reason, with or
without cause.

            (f) No supplement, modification or amendment of any term, provision
or condition of this Agreement shall be binding or enforceable unless executed
in writing by the parties hereto.

            (g) Should any part, term or provision of this Agreement or any
document required herein to be executed be declared invalid, void or
unenforceable, all remaining parts, terms and provisions hereof shall remain in
full force and effect and shall in no way be invalidated, impaired or affected
thereby.

            (h) This Agreement shall be governed by and construed and enforced
in accordance with and subject to the laws of the State of California.

        13. ARBITRATION. At the option of either party, any and all disputes or
controversies whether of law or fact and of any nature whatsoever arising from
or respecting this Agreement, except for the obligation of Purchaser to make
payment for the Stock, shall be decided by arbitration by the American
Arbitration Association in accordance with the rules and regulations of that
Association.

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           The arbitrators shall be selected as follows: In the event the
Corporation and Purchaser agree on one arbitrator, the arbitration shall be
conducted by such arbitrator. In the event the Corporation and Purchaser do not
so agree, the Corporation and Purchaser shall each select one independent,
qualified arbitrator and the two arbitrators so selected shall select the third
arbitrator. The Corporation reserves the right to object to any individual
arbitrator who shall be employed by or affiliated with a competing organization.

           Arbitration shall take place at San Francisco, California, or any
other location mutually agreeable to the parties. At the request of either
party, arbitration proceedings will be conducted in the utmost secrecy; in such
case all documents, testimony and records shall be received, heard and
maintained by the arbitrators in secrecy under seal, available for the
inspection only of the Corporation or Purchaser and their respective attorneys
and their respective experts who shall agree in advance and in writing to
receive all such information confidentially and to maintain such information in
secrecy until such information shall become generally known. The arbitrator, who
shall act by majority vote, shall be able to decree any and all relief of an
equitable nature, including but not limited to such relief as a temporary
restraining order, a temporary and/or a permanent injunction, and shall also be
able to award damages, with or without an accounting and costs. The decree or
judgment of an award rendered by the arbitrators may be entered in any court
having jurisdiction thereof.

           Reasonable notice of the time and place of arbitration shall be given
to all persons, other than the parties, as shall be required by law, in which
case such persons or those authorized representatives shall have the right to
attend and/or participate in all the arbitration hearings in such manner as the
law shall require.

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        IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the day and year first above written.

PURCHASER                                     SKYSTREAM CORPORATION
                                              a California Corporation

-------------------------------               By:
                                                 ------------------------------

                                              Title:
Address:                                            ---------------------------
        ----------------------
        ----------------------

        THIS AGREEMENT DOES NOT CONSTITUTE AN EXPRESS OR IMPLIED PROMISE OF
CONTINUED EMPLOYMENT FOR THE VESTING PERIOD OR ANY OTHER PERIOD. PURCHASER
UNDERSTANDS THAT PURCHASER'S EMPLOYMENT WITH THE CORPORATION IS ON AN "AT WILL"
BASIS, UNLESS OTHERWISE SPECIFICALLY AGREED TO BY THE CORPORATION IN WRITING.

                                CONSENT OF SPOUSE

        The undersigned spouse of Purchaser has read and hereby approves the
foregoing Agreement. In consideration of the Corporation's granting my spouse
the right to purchase the Stock as set forth in the Agreement, the undersigned
hereby agrees to be irrevocably bound by the Agreement and further agrees that
any community property interest shall be similarly bound by the Agreement. I
hereby appoint my spouse as my attorney-in-fact with respect to any amendment or
exercise of any rights under the Agreement.

                                              ---------------------------------

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                                    EXHIBIT 1

                          ELECTION UNDER SECTION 83(B)
                      OF THE INTERNAL REVENUE CODE OF 1986

The undersigned taxpayer hereby elects, pursuant to Section 83(b) of the
Internal Revenue Code of 1986 to include in Purchaser's gross income for the
current taxable year, the amount of any compensation taxable to him in
connection with Purchaser's receipt of the property described below:

1.      The name, address, taxpayer identification number and taxable year of
        the undersigned are as follows:

        NAME OF TAXPAYER:                            SPOUSE: __________________

        ADDRESS: ______________________________________________________________

        IDENTIFICATION NO. OF TAXPAYER: ____________ SPOUSE: __________________

        TAXABLE YEAR: 1996

2.      The property with respect to which the election is made is described as
        follows:

        1,000,000 shares of the Common Stock of SkyStream Corporation, a
        California corporation (the "Company").

3.      The date on which the property was transferred is: July 1, 1996

4.      The property is subject to the following restrictions:

        The right of the Company to repurchase the shares, or a portion thereof,
        upon termination of employment at a formula price. The right lapses upon
        the occurrence of certain events related to the purpose of the transfer.

5.      The value at the time of transfer, determined without regard to any
        restriction other than a restriction which by its terms will never
        lapse, of such property is: $.01 per share.

6.      The amount (if any) paid for such property: $.01 per share.

The undersigned has submitted a copy of this statement to the person for whom
the services were performed in connection with the undersigned's receipt of the
above-described property. The transferee of such property is the person
performing the services in connection with the transfer of said property.

The undersigned understands that the foregoing election may not be revoked
except with the consent of the Commissioner.

Dated:
      -----------------                          ------------------------------
                                                 Taxpayer

The undersigned spouse of taxpayer joins in this election.

Dated:
      -----------------                          ------------------------------
                                                 Spouse of Taxpayer

<PAGE>   12

                                    EXHIBIT 2

                      ASSIGNMENT SEPARATE FROM CERTIFICATE

        FOR VALUE RECEIVED and pursuant to that certain Restricted Stock
Purchase Agreement dated as of July 1, 1996 (the "Agreement") ________________
("Purchaser") hereby sells, assigns and transfers unto SkyStream Corporation
________________________________________________ (______) shares of the Common
Stock of SkyStream Corporation, a California corporation, standing in the
undersigned's name on the books of said corporation represented by certificate
No. herewith, and does hereby irrevocably constitute and appoint _______
________________ attorney to transfer the said stock on the books of the said
corporation with full power of substitution in the premises. THIS ASSIGNMENT MAY
ONLY BE USED AS AUTHORIZED BY THE AGREEMENT AND THE EXHIBITS THERETO.

Dated:                                           PURCHASER
      -----------------

                                                 Signature
                                                          ---------------------

Instruction: Please do not fill in any blanks other than the signature line. The
purpose of this assignment is to enable the Corporation to exercise its
"Purchase Option" set forth in the Agreement without requiring additional
signatures on the part of the Purchaser.

<PAGE>   13

                                    EXHIBIT 3

                            JOINT ESCROW INSTRUCTIONS

                                                                    July 1, 1996

Secretary
SkyStream Corporation
1282 Estate Drive
Los Altos, CA  94024

Dear Sir:

        As Escrow Agent for both SkyStream Corporation, a California corporation
("Corporation"), and the undersigned purchaser of stock of the Corporation
("Purchaser"), you are hereby authorized and directed to hold the documents
delivered to you pursuant to the terms of that certain Restricted Stock Purchase
Agreement ("Agreement") between the Corporation and the undersigned, to which a
copy of these Joint Escrow Instructions is attached as Exhibit 3, in accordance
with the following instructions:

        1. In the event the Corporation and/or any assignee of the Corporation
(referred to collectively for convenience herein as the "Corporation") exercises
the option set forth in Section 3 of the Agreement, the Corporation shall give
to Purchaser and you a written notice specifying the number of shares of stock
to be purchased, the purchase price, and the time for a closing hereunder at the
principal office of the Corporation. Purchaser and the Corporation hereby
irrevocably authorize and direct you to close the transaction contemplated by
such notice in accordance with the terms of said notice.

        2. At the closing, you are directed (a) to date the stock assignments
necessary for the transfer in question, (b) to fill in the number of shares of
stock being transferred, and (c) to deliver same, together with the certificate
evidencing the shares of stock to be transferred, to the Corporation against the
simultaneous delivery to you of the purchase price (by check) for the number of
shares of stock being purchased pursuant to the exercise of the Corporation's
Option.

        3. Purchaser irrevocably authorizes the Corporation to deposit with you
any certificates evidencing shares of stock (as that term is defined in the
Agreement) to be held by you hereunder pursuant to Section 10 of the Agreement.
Purchaser does hereby irrevocably constitute and appoint you as his
attorney-in-fact and agent for the term of this escrow to execute all documents
necessary or appropriate to make such securities negotiable or other property
transferable, as the case may be, and to complete any transaction herein
contemplated. Subject to the provisions of this paragraph 3, Purchaser shall
exercise all rights and privileges of a shareholder of the Corporation while the
stock is held by you.

<PAGE>   14

        4. None of the certificates representing the shares of stock deposited
under these escrow instructions shall be released to the Purchaser if such
shares of stock are subject to the Purchase Option.

        5. If at the time of termination of this escrow you should have in your
possession any documents, securities, or other property belonging to Purchaser,
you shall deliver all of same to Purchaser and all be discharged of all further
obligations hereunder.

        6. Your duties hereunder may be altered, amended, modified or revoked
only by a writing signed by all of the parties hereto.

        7. You shall be obligated only for the performance of such duties as are
specifically set forth herein and may rely and shall be protected in relying or
refraining from acting on any instrument reasonably believed by you to be
genuine and to have been signed or presented by the proper party or parties. You
shall not be personally liable for any act you may do or omit to do hereunder as
Escrow Agent or as attorney-in-fact for Purchaser while acting in good faith,
and any act done or omitted by you pursuant to the advice of your own attorneys
shall be conclusive evidence of such good faith.

        8. You are hereby expressly authorized to disregard any and all warnings
given by any of the parties hereto or by any other person or corporation,
excepting only orders or process of courts of law and of the arbitrator provided
for in Section 13 of the Agreement, and are hereby expressly authorized to
comply with and obey orders, judgments or decrees of any court and of the
arbitrator provided for in Section 13 of the Agreement. In case you obey or
comply with any such order, judgment or decree, you shall not be liable to any
of the parties hereto or to any other person, firm or corporation by reason of
such compliance, notwithstanding any such order, judgment or decree being
subsequently reversed, modified, annulled, set aside, vacated or found to have
been entered without jurisdiction.

        9. You shall not be liable in any respect on account of the identity,
authorities or rights of the parties executing or delivering or purporting to
execute or deliver the Agreement or any documents or papers deposited or called
for hereunder.

        10. You shall not be liable for the outlawing of any rights under the
Statute of Limitations with respect to these Joint Escrow Instructions or any
documents deposited with you.

        11. You shall be entitled to employ such legal counsel and other experts
as you may deem necessary properly to advise you in connection with your
obligations hereunder, may rely upon the advice of such counsel, and may pay
such counsel reasonable compensation therefor.

        12. Your responsibilities as Escrow Agent hereunder shall terminate if
you shall cease to be Secretary of the Corporation or if you shall resign by
written notice to each party. In the event of any such termination, the
Corporation shall appoint a successor Escrow Agent.

<PAGE>   15

        13. If you reasonably require other or further instruments in connection
with these Joint Escrow Instructions or obligations in respect hereto, the
necessary parties hereto shall join in furnishing such instruments.

        14. It is understood and agreed that should any dispute arise with
respect to the delivery and/or ownership or right of possession of the
securities held by you hereunder, you are authorized and directed to retain in
your possession without liability to anyone all or any part of said securities
until such disputes shall have been settled either by mutual written agreement
of the parties concerned or by a final order, decree or judgment of the
arbitrator provided for in Section 13 of the Agreement or of a court of
competent jurisdiction after the time for appeal has expired and no appeal has
been perfected, but you shall be under no duty whatsoever to institute or defend
any such proceedings.

        15. Any notice required or permitted hereunder shall be given in writing
and shall be deemed effectively given upon personal delivery or upon deposit in
the United States Post Office, by registered or certified mail with postage and
fees prepaid, addressed to each of the other parties thereunto entitled at the
following addresses, or at such other addresses as a party may designate by ten
days' advance written notice to each of the other parties hereto.

        CORPORATION:       SkyStream Corporation
                           1282 Estate Drive
                           Los Altos, CA 94024

        PURCHASER:         -------------------------
                           -------------------------
                           -------------------------

        ESCROW AGENT:      Secretary
                           SkyStream Corporation
                           1282 Estate Drive
                           Los Altos, CA  94024

        16. By signing these Joint Escrow Instructions, you become a party
hereto only for the purpose of said Joint Escrow Instructions; you do not become
a party to the Agreement.

        17. This instrument shall be binding upon and inure to the benefit of
the parties hereto, and their respective successors and permitted assigns.

                                      -3-

<PAGE>   16

                                              Very truly yours,

                                              SKYSTREAM CORPORATION,
                                              a California corporation

                                              By:
                                                 -----------------------------

                                              PURCHASER:

                                              --------------------------------

ESCROW AGENT:

------------------------------
Secretary

                                       -4-

<PAGE>   17

                                    EXHIBIT A

                       INVESTMENT REPRESENTATION STATEMENT

PURCHASER      :

SELLER         :      SKYSTREAM CORPORATION

COMPANY        :      SKYSTREAM CORPORATION

SECURITY       :      COMMON STOCK

AMOUNT         :

DATE           :

In connection with the purchase of the above-listed Securities, I, the
Purchaser, represent to the Seller and to the Company the following:

               (i) I am aware of the Company's business affairs and financial
condition, and have acquired sufficient information about the Company to reach
an informed and knowledgeable decision to acquire the Securities. I am
purchasing these Securities for my own account for investment purposes only and
not with a view to, or for the resale in connection with, any "distribution"
thereof for purposes of the Securities Act of 1933 ("Securities Act").

               (ii) I understand that the Securities have not been registered
under the Securities Act in reliance upon a specific exemption therefrom, which
exemption depends upon, among other things, the bona fide nature of my
investment intent as expressed herein. In this connection, I understand that, in
the view of the Securities and Exchange Commission ("SEC"), the statutory basis
for such exemption may be unavailable if my representation was predicated solely
upon a present intention to hold these Securities for the minimum capital gains
period specified under tax statutes, for a deferred sale, for or until an
increase or decrease in the market price of the Securities, or for a period of
one year or any other fixed period in the future.

               (iii) I further understand that the Securities must be held
indefinitely unless subsequently registered under the Securities Act or unless
an exemption from registration is otherwise available. Moreover, I understand
that the Company is under no obligation to register the Securities. In addition,
I understand that the certificate evidencing the Securities will be imprinted
with a legend which prohibits the transfer of the Securities unless they are
registered or such registration is not required in the opinion of counsel for
the Company.

<PAGE>   18

               (iv) I am familiar with the provisions of Rule 701 and Rule 144,
each promulgated under the Securities Act, which, in substance, permit limited
public resale of "restricted securities" acquired, directly or indirectly, from
the issuer thereof in a non-public offering subject to the satisfaction of
certain conditions. Rule 701 provides that if the issuer qualifies under Rule
701 at the time of issuance of the Securities, such issuance will be exempt from
registration under the Securities Act. In the event the Company later becomes
subject to the reporting requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, ninety (90) days thereafter the securities exempt under
Rule 701 may be resold, subject to the satisfaction of certain of the conditions
specified by Rule 144, including, among other things: (1) the sale being made
through a broker in an unsolicited "broker's transaction" or in transactions
directly with a market maker (as said term is defined under the Securities
Exchange Act of 1934); and, in the case of an affiliate, (2) the availability of
certain public information about the Company and the amount of securities being
sold during any three month period not exceeding the limitations specified in
Rule 144(e), if applicable. Notwithstanding this paragraph (d), I acknowledge
and agree to the restrictions set forth in paragraph (c) hereof.

               In the event that the Company does not qualify under Rule 701 at
the time of issuance of the Securities, then the Securities may be resold in
certain limited circumstances subject to the provisions of Rule 144, which
requires among other things: (1) the availability of certain public information
about the Company, (2) the resale occurring not less than two years after the
party has purchased, and made full payment for, within the meaning of Rule 144,
the securities to be sold; and, in the case of an affiliate, or of a
non-affiliate who has held the securities less than three years, (3) the sale
being made through a broker in an unsolicited "broker's transaction" or in
transactions directly with a market maker (as said term is defined under the
Securities Exchange Act of 1934) and the amount of securities being sold during
any three month period not exceeding the specified limitations stated therein,
if applicable.

               (V) I AGREE, IN CONNECTION WITH THE COMPANY'S INITIAL
UNDERWRITTEN PUBLIC OFFERING OF THE COMPANY'S SECURITIES, (1) NOT TO SELL, MAKE
SHORT SALE OF, LOAN, GRANT ANY OPTIONS FOR THE PURCHASE OF, OR OTHERWISE DISPOSE
OF ANY SHARES OF COMMON STOCK OF THE COMPANY HELD BY ME (OTHER THAN THOSE SHARES
INCLUDED IN THE REGISTRATION) WITHOUT THE PRIOR WRITTEN CONSENT OF THE COMPANY
OR THE UNDERWRITERS MANAGING SUCH INITIAL UNDERWRITTEN PUBLIC OFFERING OF THE
COMPANY'S SECURITIES FOR ONE HUNDRED EIGHTY (180) DAYS FROM THE EFFECTIVE DATE
OF SUCH REGISTRATION, AND (2) I FURTHER AGREE TO EXECUTE ANY AGREEMENT
REFLECTING (1) ABOVE AS MAY BE REQUESTED BY THE UNDERWRITERS AT THE TIME OF THE
PUBLIC OFFERING; PROVIDED, HOWEVER, THAT THE OFFICERS AND DIRECTORS OF THE
COMPANY WHO OWN THE STOCK OF THE COMPANY ALSO AGREE TO SUCH RESTRICTIONS.

               (vi) I further understand that in the event all of the applicable
requirements of Rule 144 or Rule 701 are not satisfied, registration under the
Securities Act, compliance with Regulation A, or some other registration
exemption will be required; and that, notwithstanding the fact that Rule 144 and
Rule 701 are not exclusive, the Staff of the SEC has expressed its opinion that
persons

                                      -2-

<PAGE>   19

proposing to sell private placement securities other than in a registered
offering and otherwise than pursuant to Rule 144 will have a substantial burden
of proof in establishing that an exemption from registration is available for
such offers or sales, and that such persons and their respective brokers who
participate in such transactions do so at their own risk.

               (vii) I understand that the certificate evidencing the Securities
will be imprinted with a legend which prohibits the transfer of the Securities
without the consent of the Commissioner of Corporations of California. I have
read the applicable Commissioner's Rules with respect to such restriction, a
copy of which is attached.

                                                   Signature of Purchaser:

                                                   ____________________________

                                                   Date:________________, 19___

                                       -3-<PAGE>   1

                                                                  EXHIBIT 4.5.1

                                  AMENDMENT TO
                       RESTRICTED STOCK PURCHASE AGREEMENT

        This Amendment is made as of the 7th day of February, 1997, to the
Restricted Stock Purchase Agreement dated as of July 10, 1996 (the "Agreement")
by and between SkyStream Corporation and ________________ ("Purchaser").

        1. This Amendment confirms that the Agreement is dated as of July 10,
1996.

        2. Effective upon the closing of the sale of shares of Series A
Preferred Stock pursuant to the terms of the Series A Preferred Stock Purchase
Agreement dated as of February 7, 1997 (the "Closing"), Section 6 of the
Agreement is amended to read in its entirety as follows:

6.      RESTRICTION ON TRANSFER.

        (a) Purchaser shall not sell, transfer, pledge, hypothecate or otherwise
dispose of any shares of the Stock except in accordance with (i) the terms of
this Agreement, (ii) Article VIII, Section 8.6 of the Corporation's Bylaws and
(iii) the terms of that certain Right of First Refusal and Co-Sale Agreement
dated February 7, 1997 (the "Co-Sale Agreement"). Unless prior written consent
is obtained from the Corporation or the other parties to the Co-Sale Agreement,
any transfer, sale, assignment, hypothecation, pledge, encumbrance, alienation,
or other disposition of any of the Stock, or any interest therein other than
according to the terms of this Agreement, the Bylaws and the Co-Sale Agreement,
shall be void and shall transfer no right, title or interest in or to any or all
of the Stock to the purported transferee, buyer, assignee, pledgee or
encumbrance holder.

        (b) Involuntary Transfer.

            (i) Corporation's Right to Purchase upon Involuntary Transfer. In
the event, at any time after the date of this Agreement, of any transfer by
operation of law or other involuntary transfer (including death or divorce) of
all or a portion of the Stock by the record holder thereof, the Corporation
shall have an option to purchase all of the Stock transferred at the greater of
the purchase price paid by the Purchaser pursuant to this Agreement or the fair
market value of the Stock on the date of transfer. Upon such a transfer, the
person acquiring the Stock shall promptly notify the Secretary of the
Corporation of such transfer. The right to purchase such shares of Stock shall
be provided to the Corporation for a period of twenty (20) days following
receipt by the Corporation of written notice by the person acquiring the Stock.

            (ii) Price for Involuntary Transfer. With respect to any Stock to be
transferred pursuant to Section 6(b)(i), the price per share shall be a price
set by the Board of Directors of the Corporation that will reflect the current
fair market value of the Stock in terms of present earnings and future prospects
of the Corporation. The Corporation shall notify Purchaser or his or her
executor, as

<PAGE>   2

the case may be, of the price so determined within thirty (30) days after
receipt by it of written notice of the transfer or proposed transfer of the
Stock. However, if the Purchaser does not agree with the valuation as determined
by the Board of Directors of the Corporation, the Purchaser shall be entitled to
have the valuation determined by an independent appraiser to be mutually agreed
upon by the Corporation and the Purchaser and whose fees shall be borne equally
by the Corporation and the Purchaser.

           (c) Assignment. The right of the Corporation to purchase any part of
the Stock may be assigned in whole or in part to any shareholder or shareholders
of the Corporation or other persons or organizations; provided, however, that an
assignee, other than a corporation that is the parent or 100% owned subsidiary
of the Corporation, must pay the Corporation, upon assignment of such right,
cash equal to the difference between the original purchase price and fair market
value, if the original purchase price is less than the fair market value of the
Stock subject to the assignment.

           (d) Restrictions Binding on Transferees. All transferees of Stock or
any interest therein will receive and hold such Stock or interest subject to the
provisions of this Agreement, the Bylaws of the Corporation and the Co-Sale
Agreement including, insofar as applicable, the Repurchase Option. Any sale or
transfer of the Stock shall be void unless the provisions of this Agreement, the
Bylaws and the Co-Sale Agreement are met.

        3. Section 7 of the Agreement shall be amended to read in its entirety
as follows:

           7. Termination of Rights. The restrictions set forth in Section 6 of
this Agreement shall terminate on (i) the closing date of an underwritten public
offering of Common Stock of the Corporation (the "IPO") or (ii) the closing date
of a sale of substantially all of the assets of the Corporation, purchase of
substantially all of the outstanding shares of the Corporation or merger of the
Corporation pursuant to which shareholders of this Corporation receive cash
and/or securities of a buyer whose shares are publicly traded (the
"Acquisition").

        4. Section 9 of the Agreement shall be amended to read in its entirety
as follows:

           9. Market Standoff. Purchaser hereby agrees that Purchaser shall not,
to the extent requested by the Corporation or the underwriters managing any
underwritten public offering of common stock (or other securities) of the
Corporation, offer, sell, contract to sell, make any short sale of, loan or
grant any option to purchase or otherwise dispose of any of the Stock during a
period not to exceed one hundred eighty (180) days following the effective date
of a registration statement, or such longer period as may be agreed to by the
holders of a majority of the outstanding Registrable Securities (as such term is
defined in the Rights Agreement between the Purchaser and the holders of Series
A Preferred Stock dated February 7, 1997) of the Corporation filed under the
Securities Act; provided, however, that such agreement shall be applicable only
to the first two (2) such registration statements of the Corporation which cover
shares (or other securities) to be sold on behalf of the Corporation to the
public in an underwritten public offering.

<PAGE>   3

        In order to enforce the foregoing covenant, the Corporation may impose
stop-transfer instructions with respect to the Stock of Purchaser (and the
shares or securities of every other person subject to the foregoing restriction)
until the end of such period.

        5. Except as amended herewith, all other paragraphs of the Agreement
shall continue in full force and effect. In the event of any conflict between
the provisions of the Agreement and this Amendment, the provisions of this
Amendment will govern.

        6. This Amendment, the Agreement and the documents referred to herein
constitute the entire agreement among the parties as to the matters addressed
herein and therein, including but not limited to the employment severance
benefits granted by the Corporation to the Purchaser.

<PAGE>   4

        IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
of the date and year first above written.

PURCHASER                                      SKYSTREAM CORPORATION

By                                             By
  ------------------------------                  ------------------------------
                                               Title
                                                    ----------------------------

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