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                                                                   Exhibit 10.15

                                 METRICOM, INC.

                 1993 NON-EMPLOYEE DIRECTORS' STOCK OPTION PLAN

                            ADOPTED FEBRUARY 9, 1993
                            AMENDED NOVEMBER 1, 1993
                           APPROVED DECEMBER 23, 1993
                              AMENDED JANUARY 1995
                              APPROVED MAY 16, 1995
                              AMENDED JUNE 6, 1996
                             APPROVED AUGUST 7, 1996


1. PURPOSE

         (a) The purpose of the 1993 Non-Employee Directors' Stock Option Plan
(the "Plan") is to provide a means by which each director of Metricom, Inc. (the
"Company") who is not otherwise an employee of the Company or of any Affiliate
of the Company (each such person being hereafter referred to as a "Non-Employee
Director") will be given an opportunity to purchase stock of the Company.

         (b) The word "Affiliate" as used in the Plan means any parent
corporation or subsidiary corporation of the Company as those terms are defined
in Sections 424(e) and (f), respectively, of the Internal Revenue Code of 1986,
as amended from time to time (the "Code").

         (c) The Company, by means of the Plan, seeks to retain the services of
persons now serving as Non-Employee Directors of the Company, to secure and
retain the services of persons capable of serving in such capacity, and to
provide incentives for such persons to exert maximum efforts for the success of
the Company.

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2. ADMINISTRATION

         (a) The Plan shall be administered by the Board of Directors of the
Company (the "Board") unless and until the Board delegates administration to a
committee, as provided in subparagraph 2(b).

         (b) The Board may delegate administration of the Plan to a committee
composed of not fewer than two (2) members of the Board (the "Committee"). If
administration is delegated to a Committee, the Committee shall have, in
connection with the administration of the Plan, the powers theretofore possessed
by the Board, subject, however, to such resolutions, not inconsistent with the
provisions of the Plan, as may be adopted from time to time by the Board. The
Board may abolish the Committee at any time and revest in the Board the
administration of the Plan.

3. SHARES SUBJECT TO THE PLAN

         (a) Subject to the provisions of paragraph 10 relating to adjustments
upon changes in stock, the stock that may be sold pursuant to options granted
under the Plan shall not exceed in the aggregate three hundred thousand
(300,000) shares of the Company's common stock. If any option granted under the
Plan shall for any reason expire or otherwise terminate without having been
exercised in full, the stock not purchased under such option shall again become
available for the Plan.

         (b) The stock subject to the Plan may be unissued shares or reacquired
shares, bought on the market or otherwise.

4. ELIGIBILITY

         Options shall be granted only to Non-Employee Directors of the Company.

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5. NON-DISCRETIONARY GRANTS

         (a) Each person who is first elected or appointed as a Non-Employee
Director on or after June 6, 1996 shall, upon such date of initial election or
appointment, be granted an option to purchase seven thousand (7,000) shares of
common stock of the Company on the terms and conditions set forth herein.

         (b) On January 1 of each calendar year thereafter, each person who is
serving as a Non-Employee Director shall be granted an option to purchase seven
thousand (7,000) shares of common stock of the Company on the terms and
conditions set forth herein, provided such person has continuously served as a
Non-Employee Director for at least three (3) months prior to the January 1 grant
date.

6. OPTION PROVISIONS

         Each option shall contain the following terms and conditions:

         (a) The term of each option commences on the date it is granted and,
unless sooner terminated as set forth herein, expires on the date ("Expiration
Date") ten (10) years from the date of grant. If the optionee's service as a
Non-Employee Director of the Company terminates for any reason or for no reason,
the option shall terminate on the earlier of the Expiration Date or the date
three (3) months following the date of termination of service; provided,
however, that if such termination of service is due to the optionee's death, the
option shall terminate on the earlier of the Expiration Date or eighteen (18)
months following the date of the optionee's death. In any and all circumstances,
an option may be exercised following termination of the optionee's service as a
Non-Employee Director of the Company only as to that number of shares as to
which it was exercisable on the date of termination of such service under the
provisions of subparagraph 6(e).

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         (b) Subject to subparagraph 4(b), the exercise price of each option
shall be one hundred percent (100%) of the fair market value of the stock
subject to such option on the date such option is granted.

         (c) Payment of the exercise price of each option is due in full in cash
upon any exercise.

         (d) An option shall not be transferable except by will or by the laws
of descent and distribution, and shall be exercisable during the lifetime of the
person to whom the option is granted only by such person or by his guardian or
legal representative.

         (e) The option shall become exercisable in three (3) equal annual
installments commencing on the date one (1) year after the date of grant of the
option, provided that the optionee has, during the twelve (12)-month period
prior to such annual vesting date, continuously served as a Non-Employee
Director or as an employee of or consultant to the Company or any Affiliate of
the Company, whereupon such option shall become exercisable with respect to that
portion of the shares represented by such installment.

         (f) The Company may require any optionee, or any person to whom an
option is transferred under subparagraph 6(d), as a condition of exercising any
such option: (i) to give written assurances satisfactory to the Company as to
the optionee's knowledge and experience in financial and business matters; and
(ii) to give written assurances satisfactory to the Company stating that such
person is acquiring the stock subject to the option for such person's own
account and not with any present intention of selling or otherwise distributing
the stock. These requirements, and any assurances given pursuant to such
requirements, shall be inoperative if (i) the issuance of the shares upon the
exercise of the option has been registered under a then- currently-effective
registration statement under the Securities Act of 1933, as amended (the

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"Securities Act"), or (ii), as to any particular requirement, a determination is
made by counsel for the Company that such requirement need not be met in the
circumstances under the then-applicable securities laws.

         (g) Notwithstanding anything to the contrary contained herein, an
option may not be exercised unless the shares issuable upon exercise of such
option are then registered under the Securities Act or, if such shares are not
then so registered, the Company has determined that such exercise and issuance
would be exempt from the registration requirements of the Securities Act.

7. COVENANTS OF THE COMPANY

         (a) During the terms of the options granted under the Plan, the Company
shall keep available at all times the number of shares of stock required to
satisfy such options.

         (b) The Company shall seek to obtain from each regulatory commission or
agency having jurisdiction over the Plan such authority as may be required to
issue and sell shares of stock upon exercise of the options granted under the
Plan; provided, however, that this undertaking shall not require the Company to
register under the Securities Act either the Plan, any option granted under the
Plan, or any stock issued or issuable pursuant to any such option. If the
Company is unable to obtain from any such regulatory commission or agency the
authority which counsel for the Company deems necessary for the lawful issuance
and sale of stock under the Plan, the Company shall be relieved from any
liability for failure to issue and sell stock upon exercise of such options. 

8. USE OF PROCEEDS FROM STOCK

         Proceeds from the sale of stock pursuant to options granted under the
Plan shall constitute general funds of the Company.

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9. MISCELLANEOUS

         (a) Neither an optionee nor any person to whom an option is transferred
under subparagraph 6(d) shall be deemed to be the holder of, or to have any of
the rights of a holder with respect to, any shares subject to such option unless
and until such person has satisfied all requirements for exercise of the option
pursuant to its terms.

         (b) Throughout the term of any option granted pursuant to the Plan, the
Company shall make available to the holder of such option, not later than one
hundred twenty (120) days after the close of each of the Company's fiscal years
during the option term, upon request, such financial and other information
regarding the Company as comprises the annual report to the stockholders of the
Company provided for in the Bylaws of the Company and such other information
regarding the Company as the holder of such option may reasonably request.

         (c) Nothing in the Plan or in any instrument executed pursuant thereto
shall confer upon any Non-Employee Director any right to continue in the service
of the Company or any Affiliate or shall affect any right of the Company, its
Board or stockholders or any Affiliate to terminate the service of any
Non-Employee Director with or without cause.

         (d) No Non-Employee Director, individually or as a member of a group,
and no beneficiary or other person claiming under or through him, shall have any
right, title or interest in or to any option reserved for the purposes of the
Plan except as to such shares of common stock, if any, as shall have been
reserved for him pursuant to an option granted to him.

         (e) In connection with each option made pursuant to the Plan, it shall
be a condition precedent to the Company's obligation to issue or transfer shares
to a Non-Employee Director, or to evidence the removal of any restrictions on
transfer, that such Non-Employee Director make arrangements satisfactory to the
Company to insure that the amount of any federal or other

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withholding tax required to be withheld with respect to such sale or transfer,
or such removal or lapse, is made available to the Company for timely payment of
such tax.

10. ADJUSTMENTS UPON CHANGES IN STOCK

         (a) If any change is made in the stock subject to the Plan, or subject
to any option granted under the Plan (through merger, consolidation,
reorganization, recapitalization, stock dividend, dividend in property other
than cash, stock split, liquidating dividend, combination of shares, exchange of
shares, change in corporate structure or otherwise), the Plan and all
outstanding options thereunder will be appropriately adjusted in the class(es)
and maximum number of shares subject to the Plan and the class(es) and number of
shares and price per share of stock subject to outstanding options.

         (b) In the event of: (1) a merger or consolidation in which the Company
is not the surviving corporation; (2) a reverse merger in which the Company is
the surviving corporation but the shares of the Company's common stock
outstanding immediately preceding the merger are converted by virtue of the
merger into other property, whether in the form of securities, cash or
otherwise; or (3) any other capital reorganization in which more than fifty
percent (50%) of the shares of the Company entitled to vote are exchanged, then,
to the extent permitted by applicable law, the time during which such option may
be exercised shall be accelerated and the options terminated if not exercised
prior to such event.

11. AMENDMENT OF THE PLAN

         (a) The Board at any time, and from time to time, may amend the Plan,
provided, however, that the Board shall not amend the Plan more than once every
six (6) months, with respect to the provisions of the Plan which relate to the
amount, price and timing of grants, other than to comport with changes in the
Code, the Employee Retirement Income Security Act,

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or the rules thereunder. Except as provided in paragraph 10 relating to
adjustments upon changes in stock, no amendment shall be effective unless
approved by the stockholders of the Company within twelve (12) months before or
after the adoption of the amendment, where the amendment will:

                         (i) Increase the number of shares which may be issued
under the Plan;

                         (ii) Modify the requirements as to eligibility for
participation in the Plan (to the extent such modification requires stockholder
approval in order for the Plan to comply with the requirements of Rule 16b-3);
or

                         (iii) Modify the Plan in any other way if such
modification requires stockholder approval in order for the Plan to comply with
the requirements of Rule 16b-3.

         (b) Rights and obligations under any option granted before any
amendment of the Plan shall not be altered or impaired by such amendment unless
(i) the Company requests the consent of the person to whom the option was
granted and (ii) such person consents in writing.

12. TERMINATION OR SUSPENSION OF THE PLAN

         (a) The Board may suspend or terminate the Plan at any time. Unless
sooner terminated, the Plan shall terminate on February 8, 2003. No options may
be granted under the Plan while the Plan is suspended or after it is terminated.

         (b) Rights and obligations under any option granted while the Plan is
in effect shall not be altered or impaired by suspension or termination of the
Plan, except with the consent of the person to whom the option was granted.

         (c) The Plan shall terminate upon the occurrence of any of the events
described in Section 10(b) above.

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13.      EFFECTIVE DATE OF PLAN; CONDITIONS OF EXERCISE

         (a) The Plan shall become effective upon adoption by the Board of
Directors, subject to the condition subsequent that the Plan is approved by the
stockholders of the Company.

         (b) No option granted under the Plan shall be exercised or exercisable
unless and until the condition of subparagraph 13(a) above has been met.

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