Document:

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                                                                    EXHIBIT 10.5

                                    GUARANTEE

THIS GUARANTEE (this "GUARANTEE") dated as of September 5, 2002 by Golden
Telecom, Inc., a corporation duly organized and validly existing under the laws
of the State of Delaware in the United States (the "GUARANTOR"), in favor of OAO
ROSTELECOM, a joint stock company duly organized and existing under the laws of
the Russian Federation (the "SELLER").

WHEREAS, Seller, on the one hand, and SFMT-CIS, INC., a corporation duly
organized and validly existing under the laws of the State of Delaware in the
United States ("SFMT") and OOO TELEROSS, a limited liability company duly
registered and validly existing under the laws of the Russian Federation
("TELEROSS"), each an Affiliate of the Guarantor, on the other hand, have
entered into an Ownership Interest Purchase Agreement, dated as of March 13,
2002 (as the same may be amended, modified or supplemented from time to time,
the "AGREEMENT"), providing for the sale by Seller to SFMT and TeleRoss of
Seller's 50% interest in OOO EDN Sovintel, a Russian limited liability company
(the "COMPANY");

WHEREAS, as a portion of the Purchase Price under the Agreement, TeleRoss has
agreed to issue in favor of the Seller the TeleRoss Promissory Note with a face
value equal to the Ruble equivalent of US $46,000,000;

WHEREAS, as an inducement to the Seller to enter into the Agreement, the
Guarantor has agreed to issue this Guarantee and the delivery of this Guarantee
to the Escrow Agent is a condition precedent to the Closing of the transactions
envisaged thereby; and

WHEREAS, the Guarantor will derive direct and indirect benefit from the sale by
the Seller to the Guarantor's Affiliates of the Seller's 50% interest in the
Company;

NOW, THEREFORE, in consideration of the foregoing premises and for other good
and valuable consideration, the receipt and sufficiency of which is hereby
acknowledged, the Guarantor hereby agrees as follows:

1. Definitions

          As used in this Guarantee, the terms defined in the preamble and
recitals hereto shall have the respective meanings specified therein. In
addition, capitalized terms defined in this Guarantee used and not otherwise
defined herein shall have the meanings set forth in the Agreement and the
following terms shall have the following meanings:

"Guaranteed Obligation" shall mean the obligation of TeleRoss under the TeleRoss
Promissory Note to pay an amount in Russian Rubles equal to US $46,000,000, at
the

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exchange rate established by the CBR on the payment date specified in the
TeleRoss Promissory Note all in accordance with its terms and the terms of the
Agreement.

"Non-Payment Notice" has the meaning set forth in Section 2(b).

2. Guarantee.

          (a) Subject to the terms and conditions set forth herein, the
Guarantor hereby unconditionally and irrevocably guarantees to the Seller the
payment to the Seller of the Guaranteed Obligation.

          (b) If TeleRoss fails to pay under the TeleRoss Promissory Note when
due, the Seller shall provide a notice of non-payment to the Guarantor stating
that TeleRoss has failed to make payment in full under the TeleRoss Promissory
Note on the date due (the "Non-Payment Notice"), provided however, that any
failure of the Seller to provide such Non-Payment Notice shall not affect the
Guarantor's obligations under this Guarantee.

          (c) In the event that any payment by TeleRoss under the TeleRoss
Promissory Note is rescinded or must otherwise be returned for any reason
whatsoever other than as provided for in Section 4(b)(iii), this Guarantee shall
continue to be effective, or shall be reinstated, as the case may be, and the
Guarantor shall remain liable hereunder in respect of such payment as if such
payment had not been made.

          (d) Subject to Sections 3 and 4 hereof, if the Guaranteed Obligation
shall not have been discharged by TeleRoss or any other Person in full when due,
then the Guarantor shall pay to the Seller within 15 calendar days following
receipt of the Non-Payment Notice all of the outstanding amounts due from, and
payable by, TeleRoss under the TeleRoss Promissory Note.

          (e) The Guarantor agrees to pay all reasonable fees and out-of-pocket
expenses (including reasonable attorneys' fees) incurred by the Seller and
directly relating to the enforcement by the Seller of this Guarantee in the
event of a failure to pay by the Guarantor in accordance with the terms hereof.

3. Guarantee is Limited.

          (a) Notwithstanding anything herein to the contrary, under no
circumstances shall the aggregate liability or obligations of the Guarantor
arising under this Guarantee exceed the Ruble equivalent of US $ 46,000,000, at
the exchange rate established by the CBR on the date of payment under the
TeleRoss Promissory Note plus any amounts due pursuant to Section 2(e) above.

          (b) The aggregate liability of the Guarantor arising under this
Guarantee shall be reduced to the extent of any amounts paid out by the
Guarantor to discharge any

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Lien created by the Seller with respect to the Interest prior to delivery of the
Non-Payment Notice, provided that (i) such payment has been made by the
Guarantor in good faith after final adjudication or settlement and (ii) promptly
upon the Guarantor becoming aware of any Action initiated by a third party
claiming any Lien over the Interest created by the Seller, the Guarantor shall
provide the Seller with the opportunity to participate in any such Action.

4. Effective Date; Termination.

          (a) This Guarantee and the obligations of the Guarantor hereunder
shall become effective on the Escrow Release Date. The Guarantor hereby
undertakes to provide the Seller on the Escrow Release Date with a written
confirmation stating that the Guarantee has become effective, provided however,
that any failure by the Guarantor to provide such written confirmation shall
have no effect on the effectiveness of this Guarantee.

          (b) This Guarantee, and the Guarantor's obligations hereunder in
respect of payment of the Guaranteed Obligation or otherwise, shall terminate
(i) upon satisfaction in full of the Guaranteed Obligation hereunder, or (ii) if
this Guarantee is terminated by mutual agreement of the parties to the
Agreement, or (iii) if the Agreement, or any transaction contemplated thereby,
is challenged in an Action as null and void, and as a result thereof, the
Interest is ordered in a final adjudication to be returned by any competent
Governmental Entity and the Interest is returned to the Seller.

5. Guarantee is Absolute and Unconditional.

          (a) The Guarantor hereby waives diligence, presentment, protest,
demand for payment and notice of default or nonpayment to or upon TeleRoss or
the Guarantor with respect to obligations of TeleRoss under the TeleRoss
Promissory Note or of the Guarantor under this Guaranty, as applicable.

          (b) Subject to Section 4(b) above, this Guarantee shall be construed
as a continuing, absolute and unconditional guarantee of payment without regard
to (i) the validity or enforceability of the Agreement, the TeleRoss Promissory
Note or the Guaranteed Obligation, or right to set off with respect thereto,
(ii) any defense, setoff or counterclaim (other than a defense of payment or
performance) which may at any time be available to or asserted by TeleRoss
against the Seller, or (iii) any other circumstance whatsoever (with or without
notice to or knowledge of TeleRoss or the Guarantor) which constitutes, or might
be construed to constitute, an equitable or legal discharge of TeleRoss for its
obligations under the TeleRoss Promissory Note or of the Guarantor under the
Guarantee, in bankruptcy or in any other instance.

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6. No Subrogation.

          Upon final receipt by the Seller of all amounts due and owing under
the Teleross Promissory Note, the Guarantor shall be entitled to be subrogated
to any of the rights of the Seller.

7. Miscellaneous

          Section 7.1 Amendment. This Guarantee may not be modified, amended,
terminated or revoked, in whole or in part, except by an agreement in writing
signed by Seller and the Guarantor.

          Section 7.2 Notices. All notices and other communications required or
permitted hereunder shall be in writing and shall be deemed to have been
sufficiently given to any party hereto if personally delivered or if sent by
telegram, telecopy or telex, or by registered or certified mail, return receipt
requested, or by recognized courier service, postage or other charges prepaid,
addressed as follows:

(a)      If to Seller:

         OAO Rostelecom
         Russian Federation, 125047,
         Moscow, ul. 1st Tverskaya-Yamskaya, 14
         Attention:  Kouznetsov Sergei Ivanovich
         Fax:     +7-095-787-2850
         Telephone: +7-095-787-2849

(b)      If to the Guarantor:

         Golden Telecom, Inc.
         4400 MacArthur Boulevard, N.W., Suite 200
         Washington D.C. 20007, U.S.A.
         Telephone: 1 (202) 332-5997
         Facsimile: 1 (202) 332-4877

or to such other address as may be specified from time to time by the Guarantor
or the Seller in a notice to the other party given as herein provided. Such
notice or communication will be deemed to have been given as of the date so
personally delivered, telegraphed, telecopied, telexed, mailed or sent by
courier.

          Section 7.3 Assignment. This Guarantee is provided solely for the
benefit of the Seller and may not be assigned or otherwise transferred without
the explicit consent of the Guarantor.

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          Section 7.4 Section Headings. The section headings used in this
Guarantee are for convenience of reference only and are not to affect the
construction hereof or be taken into consideration in the interpretation hereof.

          Section 7.5 Governing Law. This Agreement shall be construed and
interpreted in accordance with and governed by the laws of the State of New
York, United States of America.

          Section 7.6 Submission to Jurisdiction. The Guarantor hereby
unconditionally and irrevocably

          (a) submits to the non-exclusive general jurisdiction of the courts of
the State of New York, the courts of the United States of America for the
Southern District of New York, and appellate courts from any thereof for the
purpose of any suit, action or other proceeding arising out of this Guarantee;

          (b) consents that any such suit, action or proceeding may be brought
in such courts and waives any objection it may now or hereafter have to the
venue of any such suit, action or proceeding in any such court or that such
suit, action or proceeding was brought in an inconvenient forum and agrees not
to assert the same;

          (c) agrees that service of process in any such suit, action or
proceeding may be effected by mailing a copy thereof by registered or certified
mail, postage prepaid, to the Guarantor at its address set forth herein; and

          (d) agrees that nothing herein shall effect the right to effect
service of process in any other manner permitted by law or shall limit the right
to sue in any other jurisdiction.

IN WITNESS WHEREOF, the Guarantor has caused this Guarantee to be executed on
its behalf as of the date first written above.

                                    Golden Telecom, Inc.,

                                    ----------------------------------
                                    Name:  Alexander Vinogradov
                                    Title: President and Chief Executive Officer

                                       5<PAGE>
                                                                  EXHIBIT 10.39

                              [MOBILITY LETTERHEAD]

September 12, 2002

Jackson Walker L.L.P.
2435 N. Central Expressway, Suite 600
Richardson, Texas 75080

         Attn: Richard F. Dahlson, Partner

Dear Rick:

         Mobility Electronics, Inc., a Delaware corporation (the "Company"), and
Jackson Walker L.L.P. ("JW") are parties to a letter agreement, dated as of
August 7, 2002 (the "Prior Agreement"). This letter agreement supercedes the
Prior Agreement, and the Prior Agreement shall be deemed to be of no further
force or effect. The Company currently owes JW the sum of $868,988.69 for legal
services and fees with respect to JW's invoice numbers 694093 (dated April 26,
2002), 699105 (dated May 23, 2002), 703685 (dated June 21, 2002), 705742 (dated
July 19, 2002), 711952 (dated August 16, 2002) and 716799 (to be dated September
17, 2002) (collectively, the "Owed Fees"). The Company acknowledges and agrees
that it owes the Owed Fees to JW and has no dispute or claim against JW with
respect to the Owed Fees. The Company desires for JW to convert $600,000 of the
Owed Fees (the "Convertible Fees") into 571,428 shares (the "Shares") of common
stock, par value $0.01 per share, of Mobility (the "Common Stock"), and JW is
agreeable to such request on the terms and conditions set forth below.

         For good and valuable consideration, the receipt and sufficiency of
which are hereby acknowledged and agreed, the Company and JW hereby agree as
follows:

         1. If on or prior to December 5, 2002 (the "Deadline"), the Company has
filed a registration statement (the "Registration Statement") with the
Securities and Exchange Commission (the "SEC") which registers the resale of the
Shares by JW, and the Registration Statement has been declared effective by the
SEC (the "Effective Date"), then the Convertible Fees shall automatically be
deemed to be converted into the Shares as of the Effective Date, and within five
(5) business days after the Effective Date, the Company will cause its transfer
agent to deliver to JW a certificate representing the Shares (or, at JW's
discretion, the transfer agent will cause the Shares to be DTC transferred into
JW's brokerage account).

         2. If the Registration Statement has not been declared effective by the
SEC on or prior to December 5, 2002, then on December 6, 2002 the Company shall
wire transfer to JW the sum of $600,000 as payment for the $600,000 of the
Convertible Fees not so converted pursuant to Section 1 above.

         3. If the average closing price of the Common Stock for the period
between the Effective Date and December 31, 2002 (the "Average Closing Price"),
does not exceed $1.16 per

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Richard F. Dahlson
September 12, 2002
Page 2

share, then on or prior to January 10, 2003, the Company shall pay to JW by wire
transfer an amount equal to the difference between $1.16 and the Average Closing
Price, less an amount equal to the amounts received by JW (net of commissions)
from the sale of Shares from the Effective Date to December 31, 2002, in excess
of the product of $1.16 per Share multiplied by the number of Shares sold during
such period.

         4. On October 1, 2002, the Company shall wire transfer to JW the
$268,988.69 of the Owed Fees which are not included in the Convertible Fees.

         5. This letter may be executed in two or more counterparts, each of
which shall be deemed to be an original but all of which shall constitute one
and the same instrument. If the terms set forth in this letter agreement are
acceptable to you, please sign and date the enclosed copy of this letter and
return it to the Company.

                                             MOBILITY ELECTRONICS, INC.

                                             By: /s/ Joan W. Brubacher
                                                 ------------------------------
                                                 Joan W. Brubacher,
                                                 Chief Financial Officer

AGREED TO AND ACCEPTED
as of the date first above written:

JACKSON WALKER L.L.P.

By:  /s/ Richard F. Dahlson
     ----------------------------
     Richard F. Dahlson, Partner

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