Document:

<PAGE>   1
                                                                     EXHIBIT 4.3

                              (Face of Certificate)

                               WARRANT CERTIFICATE

               UNTIL THE SEPARATION DATE (AS DEFINED), THIS WARRANT HAS BEEN
ISSUED AS, AND MUST BE TRANSFERRED AS, A UNIT TOGETHER WITH THE ASSOCIATED 13%
SENIOR NOTES DUE 2010 OF METRICOM, INC. ("THE COMPANY") AND METRICOM FINANCE,
INC. EACH UNIT CONSISTS OF $1,000 PRINCIPAL AMOUNT OF NOTES AND A WARRANT TO
PURCHASE 4.75 SHARES OF COMMON STOCK OF THE COMPANY, SUBJECT TO ADJUSTMENT UNDER
CERTAIN CIRCUMSTANCES. A COPY OF THE WARRANT AGREEMENT PURSUANT TO WHICH THE
WARRANTS HAVE BEEN ISSUED IS AVAILABLE FROM THE COMPANY UPON REQUEST.]

               UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED
REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY ("DTC"), TO THE COMPANY OR ITS
AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY CERTIFICATE
ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS IS
REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO
CEDE & CO., OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED
REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER
HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

               TRANSFERS OF THIS GLOBAL SECURITY SHALL BE LIMITED TO TRANSFERS
IN WHOLE, BUT NOT IN PART, TO NOMINEES OF DTC OR TO A SUCCESSOR THEREOF OR SUCH
SUCCESSOR'S NOMINEE AND TRANSFERS OF PORTIONS OF THIS GLOBAL SECURITY SHALL BE
LIMITED TO TRANSFERS MADE IN ACCORDANCE WITH THE RESTRICTIONS SET FORTH IN THE
WARRANT AGREEMENT REFERRED TO HEREIN.

               THE EXERCISE OF THIS WARRANT (AND THE OWNERSHIP OF COMMON STOCK
ISSUABLE UPON THE EXERCISE THEREOF) MAY BE LIMITED BY THE COMPANY IN ORDER TO
ENSURE COMPLIANCE WITH THE RULES, REGULATIONS AND POLICIES OF THE FEDERAL
COMMUNICATIONS COMMISSION, AND THIS WARRANT WILL NOT BE EXERCISABLE BY ANY
HOLDER IF SUCH EXERCISE WOULD CAUSE THE COMPANY TO BE IN VIOLATION OF THE
COMMUNICATIONS ACT OF 1934 OR THE RULES, REGULATIONS AND POLICIES OF THE FEDERAL
COMMUNICATIONS COMMISSION.

<PAGE>   2

CUSIP 591596AH4                           No. 1  Certificate for _____ Warrants

               WARRANTS TO PURCHASE COMMON STOCK OF METRICOM, INC.

               THIS CERTIFIES THAT __________, or its registered assigns, is the
registered holder of the number of Warrants set forth above (the "Warrants").
Each Warrant entitles the holder thereof (the "Holder"), at its option and
subject to the provisions contained herein and in the Warrant Agreement referred
to below, to purchase from Metricom, Inc., a Delaware corporation (the
"Company"), 4.75 shares of Common Stock, par value of $0.001 per share, of the
Company (the "Common Stock") at the per share exercise price of $87.00 (the
"Exercise Price"), or by Cashless Exercise referred to below. This Warrant
Certificate shall terminate and become void as of the close of business on
February 15, 2010 (the "Expiration Date") or upon the exercise hereof as to all
the shares of Common Stock subject hereto. The number of shares issuable upon
exercise of the Warrants and the Exercise Price per share shall be subject to
adjustment from time to time as set forth in the Warrant Agreement.

               This Warrant Certificate is issued under and in accordance with a
Warrant Agreement dated as of February 7, 2000 (the "Warrant Agreement"),
between the Company, Bank One Trust Company, N.A. (the "Initial Warrant Agent")
and BankBoston N.A. (the "Warrant Agent," which term shall refer to the Initial
Warrant Agent from the date hereof up to and excluding the Separation Date and
thereafter, to the Warrant Agent, and includes any successor Warrant Agent under
the Warrant Agreement), and is subject to the terms and provisions contained in
the Warrant Agreement, to all of which terms and provisions the Holder of this
Warrant Certificate consents by acceptance hereof. The Warrant Agreement is
hereby incorporated herein by reference and made a part hereof. Reference is
hereby made to the Warrant Agreement for a full statement of the respective
rights, limitations of rights, duties and obligations of the Company, the
Warrant Agent and the Holders of the Warrants. Capitalized terms used but not
defined herein shall have the meanings ascribed thereto in the Warrant
Agreement. A copy of the Warrant Agreement may be obtained for inspection by the
Holder hereof upon written request prior to the Separation Date to the Warrant
Agent at Bank One Trust Company, N.A., One North State Street, 9th Floor,
Chicago, Illinois 60602, Telecopy No: 312-407-1708, Attention: Corporate Trust
Administration, and from the Separation Date, to the Warrant Agent at 150 Royal
Street, Canton, Massachusetts, 02021, Telecopy No: 781-575-2549, Attention:
Corporate Trust Department.

               Subject to the terms of the Warrant Agreement, the Warrants may
be exercised in whole or in part by presentation of this Warrant Certificate
with the Election to Purchase attached hereto duly executed and with the
simultaneous payment of the Exercise Price in cash (subject to adjustment) to
the Warrant Agent for the account of the Company at the office of the Warrant
Agent. Payment of the Exercise Price in cash shall be made by

                                        2
<PAGE>   3

certified or official bank check payable to the order of the Company or by wire
transfer of funds to an account designated by the Company for such purpose.

        This Warrant requires the Holder to comply with certain certification
and opinion delivery requirements under certain circumstances in order to
validly exercise the Warrant.

               As provided in the Warrant Agreement and subject to the terms and
conditions therein set forth, the Warrants shall be exercisable at any time on
or after August 15, 2000, provided, however, that no Warrant shall be
exercisable after February 15, 2010.

               In the event the Company enters into a Combination, the Holder
hereof will be entitled to receive upon exercise of the Warrants the kind and
amount of shares of capital stock or other securities or other property of such
surviving entity as the Holder would have been entitled to receive upon or as a
result of the Combination had the Holder exercised its Warrants immediately
prior to such Combination; provided, however, that in the event that, in
connection with such Combination, consideration to holders of Common Stock in
exchange for their shares is payable solely in cash or in the event of the
dissolution, liquidation or winding-up of the Company, the Holder hereof will be
entitled to receive such cash distributions as the Holder would have received
had the Holder exercised its Warrants immediately prior to such Combination,
less the Exercise Price.

               As provided in the Warrant Agreement, the number of shares of
Common Stock issuable upon the exercise of the Warrants and the Exercise Price
are subject to adjustment upon the happening of certain events.

               The Company may require payment of a sum sufficient to pay all
taxes, assessments or other governmental charges in connection with the transfer
or exchange of the Warrant Certificates pursuant to Section 2.6 of the Warrant
Agreement, but not for any exchange or original issuance (not involving a
transfer) with respect to temporary Warrant Certificates, the exercise of the
Warrants or the issuance of the Warrant Shares.

               Upon any partial exercise of the Warrants, there shall be
countersigned and issued to the Holder hereof a new Warrant Certificate
representing those Warrants which were not exercised. This Warrant Certificate
may be exchanged at the office of the Warrant Agent by presenting this Warrant
Certificate properly endorsed with a request to exchange this Warrant
Certificate for other Warrant Certificates evidencing an equal number of
Warrants. No fractional Warrant Shares will be issued upon the exercise of the
Warrants, but the Company shall pay an amount in cash equal to the Current
Market Value per Warrant Share on the day immediately preceding the date the
Warrant is exercised, multiplied by the fraction of a Warrant Share that would
be issuable on the exercise of any Warrant.

               All shares of Common Stock issuable by the Company upon the
exercise of the Warrants shall, upon such issue, be duly and validly issued and
fully paid and non-assessable.

                                        3
<PAGE>   4

               The holder in whose name the Warrant Certificate is registered
may be deemed and treated by the Company and the Warrant Agent as the absolute
owner of the Warrant Certificate for all purposes whatsoever and neither the
Company nor the Warrant Agent shall be affected by notice to the contrary.

               The Warrants do not entitle any holder hereof to any of the
rights of a shareholder of the Company.

               This Warrant shall be governed by the laws of the State of New
York.

               This Warrant Certificate shall not be valid or obligatory for any
purpose until it shall have been countersigned by the Warrant Agent.

                                        METRICOM, INC.

                                        By /s/ Timothy A. Dreisbach
                                           -------------------------------------
                                           Name: Timothy A. Dreisbach
                                           Title: President and CEO

DATED:

Countersigned:

/s/ Donna Fanning
--------------------------------------
BANK ONE TRUST COMPANY, N.A.
as Warrant Agent,

                                        4
<PAGE>   5

               FORM OF ELECTION TO PURCHASE WARRANT SHARES (to be
                    executed only upon exercise of Warrants)

                                 METRICOM, INC.

               The undersigned hereby irrevocably elects to exercise Warrants at
an exercise price per Warrant (subject to adjustment) of $87.00 to acquire 4.75
shares of Common Stock, par value $0.001 per share, of Metricom, Inc. on the
terms and conditions specified within the Warrant Certificate and the Warrant
Agreement therein referred to, surrenders this Warrant Certificate and all
right, title and interest therein to Metricom, Inc. and directs that the shares
of Common Stock deliverable upon the exercise of such Warrants be registered or
placed in the name and at the address specified below and delivered thereto.

Date:____________, _____

                                     -----------------------------------
                                     (Signature of Owner)

                                     -----------------------------------
                                     (Street Address)

                                     -----------------------------------
                                     (City)        (State)    (Zip Code)

                                     Signature Guaranteed by:

                                     -----------------------------------
                                     Signature must be guaranteed by an
                                     eligible Guarantor Institution (generally,
                                     banks, stock brokers, savings and
                                     loan associations and credit
                                     unions) with membership in an
                                     approved guarantee medallion
                                     program pursuant to Securities
                                     and Exchange Commission
                                     Rule 17Ad-5
--------------

The signature must correspond with the name as written upon the face of the
within Warrant Certificate in every particular, without alteration or
enlargement or any change whatsoever, and must be guaranteed.

Securities and/or check to be issued to:

                                        5
<PAGE>   6

Please insert social security or identifying number:

         Name:
              ----------------------------------------------------

         Street Address:
                        ------------------------------------------

         City, State and Zip Code:
                                  --------------------------------

Any unexercised Warrants represented by the Warrant Certificate to be issued to:
         Please insert social security or identifying number:

         Name:
              ----------------------------------------------------

         Street Address:
                        ------------------------------------------

         City, State and Zip Code:
                                  --------------------------------

                                       6<PAGE>   1
                                                                     EXHIBIT 4.4

                                 (Face of Note)

                            13% SENIOR NOTES DUE 2010

CUSIP  591596AH4                                                    No.  1
                                                                    $300,000,000

                                 METRICOM, INC.

                              METRICOM FINANCE INC.

promises to pay to Cede & Co. or registered assigns, the principal sum of Three
Hundred Million Dollars ($300,000,000) on February 15, 2010.

Interest Payment Dates:  February 15 and August 15, commencing August 15, 2000

Record Dates:  February 1 and August 1.

                                        Dated:  February 7, 2000

                                        METRICOM, INC.

                                        By: /s/ James E. Wall
                                           -------------------------------------
                                        Name: James E. Wall
                                        Title: Chief Financial Officer

                                        METRICOM FINANCE, INC.

                                        By: /s/ James E. Wall
                                           -------------------------------------
                                        Name: James E. Wall
                                        Title: Chief Financial Officer

This is the Global Note referred to in
the within-mentioned Indenture:

BANK ONE TRUST COMPANY, N.A.,
as Trustee

By: /s/ Sandra L. Caruba
   -----------------------------------
Authorized Signatory

<PAGE>   2

                                 (BACK OF NOTE)
================================================================================

                            13% Senior Notes due 2010

THIS GLOBAL NOTE IS HELD BY THE DEPOSITARY (AS DEFINED IN THE INDENTURE
GOVERNING THIS NOTE) OR ITS NOMINEE IN CUSTODY FOR THE BENEFIT OF THE BENEFICIAL
OWNERS HEREOF, AND IS NOT TRANSFERABLE TO ANY PERSON UNDER ANY CIRCUMSTANCES
EXCEPT THAT (I) THE TRUSTEE MAY MAKE SUCH NOTATIONS HEREON AS MAY BE REQUIRED
PURSUANT TO SECTION 2.07 OF THE INDENTURE, (II) THIS GLOBAL NOTE MAY BE
DELIVERED TO THE TRUSTEE FOR CANCELLATION PURSUANT TO SECTION 2.11 OF THE
INDENTURE AND (III) THIS GLOBAL NOTE MAY BE TRANSFERRED TO A SUCCESSOR
DEPOSITARY WITH THE PRIOR WRITTEN CONSENT OF THE COMPANY.

UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR NOTES IN DEFINITIVE
FORM, THIS NOTE MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITARY TO A
NOMINEE OF THE DEPOSITARY OR BY A NOMINEE OF THE DEPOSITARY TO THE DEPOSITARY OR
ANOTHER NOMINEE OF THE DEPOSITARY OR BY THE DEPOSITARY OR ANY SUCH NOMINEE TO A
SUCCESSOR DEPOSITARY OR A NOMINEE OF SUCH SUCCESSOR DEPOSITARY. UNLESS THIS
CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST
COMPANY (55 WATER STREET, NEW YORK, NEW YORK) ("DTC"), TO THE COMPANY OR ITS
AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY CERTIFICATE
ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS MAY BE
REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO
CEDE & CO. OR SUCH OTHER ENTITY AS MAY BE REQUESTED BY AN AUTHORIZED
REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER
HEREOF, CEDE & CO., HAS AN INTEREST HEREIN

UNTIL THE SEPARATION DATE (AS DEFINED), THIS NOTE HAS BEEN ISSUED WITH, AND MUST
BE TRANSFERRED WITH, THE ASSOCIATED WARRANTS TO PURCHASE COMMON STOCK OF THE
COMPANY. EACH $1,000 PRINCIPAL AMOUNT OF NOTES IS ASSOCIATED WITH A WARRANT TO
PURCHASE 4.75 SHARES OF COMMON STOCK, SUBJECT TO ADJUSTMENT UNDER CERTAIN
CIRCUMSTANCES. A COPY OF THE WARRANT AGREEMENT PURSUANT TO WHICH THE WARRANTS
HAVE BEEN ISSUED IS AVAILABLE FROM THE COMPANY UPON REQUEST.

FOR PURPOSES OF SECTION 1273 OF THE INTERNAL REVENUE CODE OF 1986, AS AMENDED
(THE "CODE"), THIS SECURITY HAS ORIGINAL ISSUE

                                        2
<PAGE>   3

DISCOUNT. FOR PURPOSES OF SECTION 1273 OF THE CODE, THE ISSUE PRICE IS $787.94
AND THE AMOUNT OF ORIGINAL ISSUE DISCOUNT IS $212.06, IN EACH CASE PER $1,000
PRINCIPAL AMOUNT OF THIS SECURITY. FOR PURPOSES OF SECTION 1275 OF THE CODE, THE
YIELD TO MATURITY COMPOUNDED SEMIANNUALLY IS 17.57%.

               Capitalized terms used herein shall have the meanings assigned to
them in the Indenture referred to below unless otherwise indicated.

        1. INTEREST. Metricom Inc., a Delaware corporation (the "Company"), and
Metricom Finance, Inc. ("Finance Sub," and together with the Company, the
"Co-Obligors") promises to pay interest on the principal amount of this Note at
13% per annum from February 7, 2000 until maturity. The Issuers will pay
interest semi-annually on February 15 and August 15 of each year, or if any such
day is not a Business Day, on the next succeeding Business Day (each an
"Interest Payment Date"). Interest on the Notes will accrue from the most recent
date to which interest has been paid or, if no interest has been paid, from the
date of issuance; provided, however, that if there is no existing Default in the
payment of interest, and if this Note is authenticated between a record date
referred to on the face hereof and the next succeeding Interest Payment Date,
interest shall accrue from such next succeeding Interest Payment Date; provided,
further, that the first Interest Payment Date shall be August 15, 2000. The
Issuers shall pay interest (including post-petition interest in any proceeding
under any Bankruptcy Law) on overdue principal and premium, if any, from time to
time on demand at a rate that is 1% per annum in excess of the rate then in
effect; it shall pay interest (including post-petition interest in any,
proceeding under any Bankruptcy Law) on overdue installments of interest
(without regard to any applicable grace periods) from time to time on demand at
the same rate to the extent lawful. Interest will be computed on the basis of a
360-day year of twelve 30-day months.

        2. METHOD OF PAYMENT. The Issuers will pay interest on the Notes (except
defaulted interest) to the Persons who are registered Holders of Notes at the
close of business on each February 1 or August 1 immediately preceding the next
Interest Payment Date, even if such Notes are cancelled after such record date
and on or before such Interest Payment Date, except as provided in Section 2.12
of the Base Indenture with respect to defaulted interest. The Notes will be
payable as to principal, premium and interest at the office or agency of the
Issuers maintained for such purpose within or without the City and State of New
York, or, at the option of the Issuers, payment of interest may be made by check
mailed to the Holders at their addresses set forth in the register of Holders;
provided, however, that payment by wire transfer of immediately available funds
will be required with respect to principal of and interest and premium and on,
the Global Note and all other Notes, the Holders of which shall have provided
wire transfer instructions to the Issuers or the Paying Agent. Such payment
shall be in such coin or currency of the United States of America as at the time
of payment is legal tender for payment of public and private debts.

        3. PAYING AGENT AND REGISTRAR. Initially, Bank One Trust Company, N.A.,
the Trustee under the Indenture, will act as Paying Agent and Registrar. The
Issuers may

                                        3
<PAGE>   4

change any Paying Agent or Registrar without notice to any Holder. The Issuers
or any of their Subsidiaries may act in any such capacity.

        4. INDENTURE. The Issuers issued the Notes under an Indenture dated as
of December 29, 1999, between each of the Issuers and the Trustee (the "Base
Indenture"), as supplemented by the First Supplemental Indenture thereto, dated
February 7, 2000 (as supplemented, the "Indenture"). The terms of the Notes
include those stated in the Indenture and those made part of the Indenture by
reference to the Trust Indenture Act of 1939, as amended (15 U.S. Code Sections
77aaa-77bbbb). The Notes are subject to all such terms, and Holders are referred
to the Indentures and such Act for a statement of such terms. To the extent any
provision of this Note conflicts with the express provisions of the Indenture,
the provisions of the Indenture shall govern and be controlling. The Notes are
obligations of the Issuers limited to $300,000,000 in aggregate principal
amount.

        5. RELEASE OF OBLIGATIONS FOLLOWING HOLDING COMPANY REORGANIZATION. Upon
consummation of the Holding Company Reorganization, the obligation of (a)
Finance Sub with respect to the Notes shall automatically be extinguished and
only the Company shall continue as the sole obligor on the Senior Notes, if the
Holding Company Reorganization is one in which the assets and operations of the
Company are transferred to Finance Sub or any of its Restricted Subsidiaries, as
contemplated by clause (1) of the definition of Holding Company Reorganization,
or (b) the Company with respect to the Notes shall automatically be extinguished
and only Finance Sub shall continue as the sole obligor on the Notes, if the
Holding Company Reorganization is one in which the assets and operations of the
Company remain with the Company or its successor corporation or organization, as
contemplated by clause (2) of the definition of Holding Company Reorganization;
provided, however, that upon consummation of the Holding Company Reorganization,
the Company's guarantee of Finance Sub's obligations with respect to the Notes
shall automatically, and without further notice to or action by the Holders, be
extinguished and shall cease to be of any further force or effect. In that
event, the Trustee shall, at the request of either obligor, enter into a
Supplemental Indenture to evidence the release of the Company or Finance Sub, as
the case may be, from its obligations on the notes, and the release of the
Company from its guarantee of Finance Sub's obligations with respect to the
Notes.

                                        4
<PAGE>   5

        6. OPTIONAL REDEMPTION. On or after February 15, 2005, the Issuers may
redeem the Notes at any time, in whole or in part, upon not less than 30 nor
more than 60 days' notice, at the redemption prices (expressed as percentages of
principal amount) set forth below, plus accrued and unpaid interest, if any,
thereon to the date fixed for redemption, if redeemed during the twelve-month
period beginning on February 15 of the years indicated below:

<TABLE>
<CAPTION>
         YEAR                                     PERCENTAGE
         ----                                     ----------
<S>                                               <C>
         2005                                      108.000
         2006                                      106.000
         2007                                      104.000
         2008                                      102.000
         2009 and thereafter                       100.000
</TABLE>

        7. MANDATORY REDEMPTION. Except as set forth in paragraph 7 below, the
Issuers shall not be required to make mandatory redemption payments with respect
to the Notes.

        8.REPURCHASE AT OPTION OF HOLDER. If there is a Change of Control, each
Holder will have the right to require the Issuers to repurchase all or any part
of such Holder's Notes pursuant to the Change of Control Offer described below,
in accordance with Section 4.14 of the First Supplemental Indenture, at a
purchase price in cash (the "Change of Control Payment") equal to 101% of the
principal amount of such Notes, plus accrued and unpaid interest to the Change
of Control Payment Date. Within 10 days following any Change of Control, the
Issuers shall mail a notice to the Trustee and each Holder describing the
transaction or transactions that constitute the Change of Control and offering
to repurchase the Notes (the "Change of Control Offer") on the date specified in
the notice, which will not be earlier than 30 days or later than 60 days from
the date the notice is mailed (the "Change of Control Payment Date"), in
accordance with Section 4.14 of the First Supplemental Indenture.

If either of the Issuers or a Restricted Subsidiary consummates any Asset Sales,
when the aggregate amount of Excess Proceeds exceeds $10.0 million, the Issuers
shall make an offer to all Holders and holders of any other Indebtedness that
ranks equally in right of payment with the Notes and that requires the Issuers
to make such an offer (an "Asset Sale Offer") to purchase the maximum principal
amount or principal amount at maturity, as applicable, of Notes and other
Indebtedness that ranks equally in right of payment with the Notes that may be
purchased out of the Excess Proceeds, at an offer price in cash in an amount
equal to 100% of the principal amount of the Senior Notes, plus accrued and
unpaid interest, if any, to the purchase date in accordance with Section 4.07 of
the First Supplemental Indenture.

        9. NOTICE OF REDEMPTION. Notice of redemption will be mailed at least 30
days but not more than 60 days before the redemption date to each Holder whose
Notes are to be redeemed at its registered address. Notes in denominations
larger than $1,000 may be

                                        5
<PAGE>   6

redeemed in part but only in whole multiples of $1,000, unless all of the Notes
held by a Holder are to be redeemed. On and after the redemption date interest
ceases to accrue on Notes or portions thereof called for redemption.

        10. DENOMINATIONS, TRANSFER, EXCHANGE. The Notes are in registered form
without coupons in denominations of $1,000 and integral multiples of $1,000. The
transfer of Notes may be registered and Notes may be exchanged as provided in
the Indenture. The Registrar and the Trustee may require a Holder, among other
things, to furnish appropriate endorsements and transfer documents and the
Issuers may require a Holder to pay any taxes and fees required by law or
permitted by the Indenture. The Issuers need not exchange or register the
transfer of any Note or portion of a Note selected for redemption, except for
the unredeemed portion of any Note being redeemed in part. Also, the Issuers
need not exchange or register the transfer of any Notes for a period of 15 days
before a selection of Notes to be redeemed or during the period between a record
date and the corresponding interest payment date.

        11. PERSONS DEEMED OWNERS. The registered Holder of a Note may be
treated as its owner for all purposes.

        12. AMENDMENT, SUPPLEMENT AND WAIVER. Subject to certain exceptions, the
Indenture or the Notes may be amended or supplemented with the consent of the
Holders of at least a majority in principal amount of the then outstanding Notes
voting as a single class, and any existing default or compliance with any
provision of the Indenture or the Notes may be waived with the consent of the
Holders of a majority in principal amount of the then outstanding Notes voting
as a single class. Without the consent of any Holder of a Note, the Indenture or
the Notes may be amended or supplemented to cure any ambiguity, defect or
inconsistency, to provide for uncertificated Notes in addition to or in place of
certificated Notes, to provide for the assumption of the Issuers' obligations to
Holders of the Notes in case of a merger or consolidation, or sale of
substantially all of the Company's assets to make any change that would provide
any additional rights or benefits to the Holders of the Notes or that does not
adversely affect the legal rights under the Indenture of any such Holder, to
comply with the requirements of the Commission in order to effect or maintain
the qualification of the Indenture under the Trust Indenture Act.

        13. DEFAULTS AND REMEDIES. Events of Default include: (a) default in the
payment of interest on the Notes when due and payable and, other than with
respect to the first four scheduled interest payments on the Notes, continuance
of such default for a period of 30 days; (b) default in the performance of any
covenant set forth in the Pledge Agreement, or repudiation by the Issuers of any
of their obligations under the Pledge Agreement or the unenforceability of the
Pledge Agreement against the Issuers for any reason which in any one case or in
the aggregate results in a material impairment of the rights intended to be
afforded thereby; (c) default when due in the payment of principal of, or
premium, if any, on any Note; (d) failure by the Issuers or any of their
Restricted Subsidiaries for 30 days after written notice to them by the Trustee
or by the Holders of at least 25% in aggregate principal amount of the
outstanding Notes to comply with the provisions of Section 4.03, 4.04, 4.07 or
4.14 hereof; (e) failure by the Issuers or any of

                                        6
<PAGE>   7

their Restricted Subsidiaries to perform or comply with the provisions of
Article 5 hereof or of the Indenture; (f) failure by the Issuers or any of their
Restricted Subsidiaries for 60 days after written notice to them by the Trustee
or by the Holders of at least 25% in aggregate principal amount of the
outstanding Notes to comply with any other covenant set forth in this Note or
the Indenture; (g) default under any mortgage, indenture or instrument under
which there may be issued or by which there may be secured or evidenced any
Indebtedness for money borrowed by the Issuers or any of their Significant
Subsidiaries (or group of Restricted Subsidiaries that if treated as a single
subsidiary would constitute a Significant Subsidiary), or the payment of which
is guaranteed by the Issuers or any of their Significant Subsidiaries (or group
of Restricted Subsidiaries that if treated as a single subsidiary would
constitute a Significant Subsidiary), whether that Indebtedness or guarantee now
exists or is created after the date hereof, which default (1) is caused by a
failure to pay principal of or premium, if any, or interest on that Indebtedness
prior to the expiration of the grace period provided in that Indebtedness on the
date of such default (a "Payment Default") or (2) results in the acceleration of
that Indebtedness prior to its express maturity, and, in each case, if the
principal amount of any such Indebtedness, together with the principal amount of
any other such Indebtedness under which there has been a Payment Default or the
maturity of which has been so accelerated, aggregates $10.0 million or more; (h)
failure by the Issuers or any of their Significant Subsidiaries (or group of
Restricted Subsidiaries that if treated as a single subsidiary would constitute
a Significant Subsidiary) to pay final judgments aggregating in excess of $10.0
million, excluding amounts covered by insurance, which judgments are not paid,
discharged or stayed for a period of 60 days after the date on which the right
to appeal has expired; (i) an Issuer or any Significant Subsidiaries of an
Issuer (or any group of Subsidiaries that if treated as a single subsidiary
would constitute a Significant Subsidiary): (1) commences a voluntary case under
any Bankruptcy Law; (2) consents to the entry of an order for relief against it
in an involuntary case now or hereafter in effect; (3) consents to the
appointment of a custodian of such Issuer or any Significant Subsidiary of such
Issuer (or group of Restricted Subsidiaries that if treated as a single
Subsidiary would constitute a Significant Subsidiary) or for all or
substantially all of the property and assets of an Issuer or any Significant
Subsidiary of such Issuer (or group of Restricted Subsidiaries that if treated
as a single Subsidiary would constitute a Significant Subsidiary); or (4)
effects a general assignment for the benefit of its creditors; or (j) a court of
competent jurisdiction enters an order or decree under any Bankruptcy Law for:
(1) relief in respect of an Issuer or any Significant Subsidiary of an Issuer
(or any group of Subsidiaries that, taken as a whole, would constitute a
Significant Subsidiary) in an involuntary case under any Bankruptcy Law now or
hereafter in effect; (2) appointment of a custodian of an Issuer or any
Significant Subsidiary of an Issuer (or any group of Subsidiaries that if
treated as a single subsidiary would constitute a Significant Subsidiary) or for
all or substantially all of the property and assets of an Issuer or any
Significant Subsidiary (or any group of Subsidiaries that if treated as a single
subsidiary would constitute a Significant Subsidiary); or (3) the winding up or
liquidation of the affairs of an Issuer or any Significant Subsidiary or any
group of Subsidiaries that, taken as a whole, would

                                        7
<PAGE>   8

constitute a Significant Subsidiary; and, in each case, the order or decree
remains unstayed and in effect for a period of 60 consecutive days.

        14. TRUSTEE DEALINGS WITH ISSUERS. The Trustee, in its individual or any
other capacity, may make loans to, accept deposits from, and perform services
for the Issuers or their Affiliates, and may otherwise deal with the Issuers or
their Affiliates, as if it were not the Trustee.

        15. NO RECOURSE AGAINST OTHERS. No director, officer, employee,
incorporator or stockholder, of the Issuers, as such, shall have any liability
for any obligations of the Issuers under the Notes or the Indenture or for any
claim based on, in respect of, or by reason of, such obligations or their
creation. Each Holder by accepting a Note waives and releases all such
liability. The waiver and release are part of the consideration for the issuance
of the Notes such waiver may not be effective to waive liabilities under the
federal securities laws and it is the view of the SEC that such a waiver is
against public policy.

        16. AUTHENTICATION. This Note shall not be valid until authenticated by
the manual signature of the Trustee or an authenticating agent.

        17. ABBREVIATIONS. Customary abbreviations may be used in the name of a
Holder or an assignee, such as: TEN COM (= tenants in common), TEN ENT (=
tenants by the entireties), JT TEN (= joint tenants with right of survivorship
and not as tenants in common), CUST (= Custodian), and U/G/M/A (= Uniform Gifts
to Minors Act).

        18. CUSIP NUMBERS. Pursuant to a recommendation promulgated by the
Committee on Uniform Security Identification Procedures, the Issuers have caused
CUSIP numbers to be printed on the Notes and the Trustee may use CUSIP numbers
in notices of redemption as a convenience to Holders. No representation is made
as to the accuracy of such numbers either as printed on the Notes or as
contained in any notice of redemption and reliance may be placed only on the
other identification numbers placed thereon.

The Issuers will furnish to any Holder upon written request and without charge a
copy of the Indenture. Requests may be made to:

Metricom, Inc.
Metricom Finance, Inc.
980 University Avenue
Los Gatos, California 95032
Attention:  Chief Financial Officer

                                        8
<PAGE>   9

                                 ASSIGNMENT FORM

To assign this Note, fill in the form below:

(I) or (we) assign and transfer this Note to

                  (Insert assignee's soc. sec. or tax I.D. no.)

              (Print or type assignee's name, address and zip code)

and irrevocably appoint

to transfer this Note on the books of the Issuers. The agent may substitute
another to act for him.

Date:                                   Your Signature:
     --------------------------                        -------------------------

(Sign exactly as your name appears on the face of this Note)

Signature Guarantee:
                    -----------------------

                                        9
<PAGE>   10

                       OPTION OF HOLDER TO ELECT PURCHASE

               If you want to elect to have this Note purchased by the Issuers
pursuant to Section 4.07 or 4.14 of the Indenture, check the box below:

               Section 4.07

               Section 4.14

               If you want to elect to have only part of the Note purchased by
the Issuers pursuant to Section 4.07 or Section 4.14 of the Indenture, state the
amount you elect to have purchased: $________

Date:                                   Your Signature:
     --------------------------                        -------------------------

(Sign exactly as your name appears on the Note)

Signature Guarantee:
                    -------------------------
Tax Identification No:

                                       10
<PAGE>   11

              SCHEDULE OF EXCHANGES OF INTERESTS IN THE GLOBAL NOTE

               The following exchanges of a part of this Global Note for an
interest in a Definitive Note, or exchanges of a part of a Definitive Note for
an interest in this Global Note, have been made:

<TABLE>
<CAPTION>
                                                        Principal Amount
                     Amount of     Amount of increase       of this
                    decrease in       in Principal        Global Note        Signature of
                  Principal Amount       Amount         following such    authorized officer
                      of this           of this          decrease (or     of Trustee or Note
 Date of Exchange   Global Note       Global Note          increase)           Custodian
-----------------------------------------------------------------------------------------------
<S>               <C>              <C>                  <C>               <C>

</TABLE>

                                       11

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