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                                  EXHIBIT 10.20

FORM OF CHANGE OF CONTROL PROVISION FOR OFFICERS:

If, within the thirteen (13) months following a Trigger Event (defined below),
Purchaser's service as an Employee is either (1) Involuntarily Terminated
Without Cause or (2) Constructively Terminated, then the Repurchase Option shall
lapse in full as to [ALTERNATIVES: all (for CEO, CFO and General Counsel) or one
half (for all other vice presidents)] of the shares that are subject to such
Repurchase Option on the date of such termination of service as an Employee.
However, if the benefit Purchaser would receive from such lapse of the
Repurchase Option by itself or when combined with any other payment or benefit
Purchaser receives (each a "Payment") would (i) constitute a "parachute payment"
within the meaning of Section 280G of the Internal Revenue Code of 1986, as
amended (the "Code"), and (ii) but for this sentence, be subject to the excise
tax imposed by Section 4999 of the Code (the "Excise Tax"), then the aggregate
value of such Payments shall be either (x) the full amount of such Payment or
(y) such lesser amount (any Payment in cash being reduced first and the order in
reduction of other Payments to be determined so as to provide the greatest
reduction in the amount subject to the Excise Tax with the least reduction in
the aggregate amount of Payments) as would result in no portion of the Payments
being subject to the Excise Tax, whichever of the foregoing amounts, taking into
account the applicable federal, state and local employment taxes, income taxes,
and the Excise Tax results in Purchaser's receipt, on an after-tax basis, of the
greater amount of the Payments notwithstanding that all or some portion of the
Payments may be subject to the Excise Tax. Purchaser shall be solely responsible
for the payment of all personal tax liability that is incurred as a result of
the payments and benefits received under this provision, and Purchaser will not
be reimbursed by the Company for any such payments.

"PARACHUTE PAYMENT" CALCULATION AND ADJUSTMENT. All determinations required to
be made under this Section __ regarding whether a Payment is a "parachute
payment" shall be made by the Company's independent auditors. Such auditors
shall provide detailed supporting calculations both to the Company and Purchaser
within fifteen (15) business days of the date that Purchaser's status as an
Employee terminates or such earlier time as is requested by the Company. For
purposes of making the calculations required by this Section __, the auditors
may make reasonable assumptions and approximations concerning applicable taxes
and may rely on reasonable, good faith determinations concerning the application
of the Code. The Company and Purchaser shall furnish to the auditors such
information and documents as the auditors may reasonably request in order to
make a determination under this Section __. The Company shall bear all costs the
auditors may reasonably incur in connection with any calculations contemplated
by this Section __. Any such determination by the Company's independent auditors
shall be binding upon the Company and Purchaser. Within five (5) days after
receipt of the calculations, the Company shall pay to or distribute to or for
the benefit of Purchaser such amounts as are then due to Purchaser under this
Agreement. As a result of the uncertainty in the application of Section 280G of
the Code at the time of the initial determination by the Company's independent
auditors hereunder, it is possible that a Payment or Payments, as the case may
be, will have been made by the Company that should not have been made
("Overpayment") or that an additional Payment or Payments, as the case may be,
which will not have been made by the Company could have been made
("Underpayment"), in each case, consistent with the calculations required to be
made hereunder. In the event that the Company's independent auditors, based upon
the assertion of the deficiency by the Internal Revenue Service against
Purchaser or the Company that the Company's independent auditors believe has a
high probability of success, determine that an Overpayment has been made, any
such overpayment paid or distributed by the Company to or for the benefit of
Purchaser shall be treated for all purposes as a loan AB INITIO to Purchaser
that Purchaser shall repay to the Company together with interest at the
applicable federal rate provided for in Section 7872(f)(2) of the Code; provided
however, that no such loan shall be deemed to have been made and no amount shall
be payable by Purchaser to the Company if and to the extent such deemed loan and
payment would not either reduce the amount on which Purchaser is subject to tax
under Section 1 and Section 4999 of the Code or generate a refund of such taxes.
In the event that the Company's independent auditors, based upon controlling
precedent or other substantial authority, determine that an Underpayment has
occurred, any such Underpayment shall be promptly paid by the Company to or for
the benefit of Purchaser together with interest at the applicable federal rate
provided for in Section 7872(f)(2) of the Code.

CONSTRUCTIVELY TERMINATED. For purposes of this Section __, Constructively
Terminated shall mean the voluntary termination by Purchaser of Purchaser's
service as an Employee after any of the following are undertaken without
Purchaser's express written consent: (a) the assignment to Purchaser of any
duties or responsibilities which result in a material diminution or adverse
change of Purchaser's position, status or circumstances of employment, but shall
not include a mere change in title or reporting relationship; (b) reduction in
Purchaser's base salary to less than Purchaser's base salary as in effect
immediately prior to the transaction; (c) any failure by the Company to continue
in effect any benefit plan or arrangement, including incentive plans or plans to
receive securities of the

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Company, in which Purchaser is participating (hereinafter referred to as
"Benefit Plans"), or the taking of any action by the Company which would
adversely affect Purchaser's participation in or reduce Purchaser's benefits
under any Benefit Plans or deprive Purchaser of any fringe benefit then
enjoyed by Purchaser, PROVIDED, HOWEVER, that Purchaser's termination is not
deemed to be Constructively Terminated if the Company offers a range of
benefit plans and programs which, taken as a whole, are comparable to the
Benefit Plans; (d) a relocation of Purchaser's office at which Purchaser
principally performs duties or the Company's principal business offices, if
Purchaser's principal office is at such offices, to a location more than
thirty-five (35) miles from the location at which Purchaser performs duties
prior to the Trigger Event, except for required travel by Purchaser on the
Company's business to an extent substantially consistent with Purchaser's
business travel obligations at the time of a Trigger Event; (e) any material
breach by the Company of any agreement between Purchaser and the Company
concerning Purchaser's employment; or (f) any failure by the Company to
obtain the assumption of any material agreement between Purchaser and the
Company concerning Purchaser's employment by any successor or assign of the
Company.

INVOLUNTARILY TERMINATED WITHOUT CAUSE. For purposes of this Section __,
Involuntarily Terminated Without Cause shall mean dismissal or discharge of
Purchaser for any reason other than Cause, death or disability. For purposes
herein, "Cause" means reasonable belief that Purchaser has committed one or more
of the following: (i) conviction of any felony or any crime involving moral
turpitude or dishonesty; (ii) participation in a fraud, misappropriation, or
embezzlement of Company funds or property or act of dishonesty against the
Company; (iii) material breach of the Company's policies, provided that the
Company has given Purchaser written notification of the breach and has provided
Purchaser with fifteen (15) days' opportunity to cure the breach; (iv) willful
conduct or gross negligence which is materially injurious to the reputation,
business or business relationships of the Company or results in material damage
to the Company's property; or (v) material breach of the Proprietary Information
and Inventions Agreement between Purchaser and the Company.

TRIGGER EVENT. For purposes of this Section __, Trigger Event shall mean a
transaction described in subparts (ii) and (iii) of subsection 11(c) of the Plan
in which the Company's stockholders immediately prior to such transaction do not
wield more than fifty percent (50%) of the voting power entitled to vote for
either Directors or members of the board of directors of the Company's ultimate
parent corporation immediately after such transaction. Any person who acquired
voting securities of the Company prior to the occurrence of a transaction
described in subparts (ii) and (iii) of subsection 11(c) of the Plan in
contemplation of such transaction, and who immediately after such transaction
possesses direct or indirect beneficial ownership of at least ten percent (10%)
of such voting power shall not be included in the group of stockholders of the
Company immediately prior to such transaction.

SHARES REPURCHASABLE AT PURCHASER'S ORIGINAL EXERCISE PRICE. The Company may
repurchase all or any of the Unvested Shares at a price ("Option Price") equal
to the Purchaser's Exercise Price for such shares of ______ dollars ($_______)
per share as indicated on Purchaser's Stock Option Grant Notice.

EXERCISE OF REPURCHASE OPTION. The Repurchase Option shall be exercised by
written notice signed by an Officer of the Company and delivered or mailed as
provided herein. Such notice shall identify the number of shares of Common Stock
to be purchased and shall notify Purchaser of the time, place and date for
settlement of such purchase, which shall be scheduled by the Company within the
term of the Repurchase Option set forth above. The Company shall be entitled to
pay for any shares of Common Stock purchased pursuant to its Repurchase Option
at the Company's option in cash or by offset against any indebtedness owing to
the Company by Purchaser (including without limitation any Note given in payment
for the Common Stock), or by a combination of both. Upon delivery of such notice
and payment of the purchase price in any of the ways described above, the
Company shall become the legal and beneficial owner of the Common Stock being
repurchased and all rights and interest therein or related thereto, and the
Company shall have the right to transfer to its own name the Common Stock being
repurchased by the Company, without further action by Purchaser.