Document:

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                                                                   Exhibit 10.75

                       KEY MANAGEMENT RETENTION AGREEMENT

        THIS KEY MANAGEMENT RETENTION AGREEMENT (the "Agreement"), dated as of
February 6, 2002 (the "Effective Date"), is made and entered into by and between
RAYTEL MEDICAL CORPORATION, a Delaware corporation (the "Company"), and SWAPAN
SEN (the "Executive").

                                    RECITALS:

        A. The Executive is currently employed as the Company's Senior Vice
President, and President of the Company's subsidiary, Raytel Imaging Holdings,
Inc. ("RIH"), pursuant to a written employment agreement dated as of March 1,
1998 (the "Employment Agreement");

        B. The Company is considering various potential strategic transactions
that could result in a Change of Control (as hereinafter defined);

        C. Pursuant to a resolution adopted on December 19, 2001, the Board of
Directors approved a supplement to the Employment Agreement to provide
additional incentive for the continued employment of the Executive in order to
facilitate a potential Change of Control; and

        D. The parties now desire to enter into an agreement confirming such
incentive arrangements.

        NOW, THEREFORE, the parties agree as follows:

        1. Definitions. For purposes of this Agreement, the following terms
shall be defined as follows:

               1.1 "Cause" shall exist in the event of the Executive's (i)
willful and repeated neglect of his duties as an employee of the Company (other
than as a result of a physical disability not related to substance abuse), (ii)
conviction of a crime involving moral turpitude, (iii) commission of any act of
fraud or dishonesty against the Company, or (iv) breach of the Executive's
obligations under the Employment Agreement or the Proprietary Information and
Inventions Agreement between the Executive and the Company which, if curable, is
not cured within ten (10) days following notice of such breach by the Company.

               1.2 A "Change of Control" of the Company shall occur upon: (i) a
merger, consolidation or other reorganization involving the Company, or a tender
offer, exchange offer or other transaction or series of transactions involving
the acquisition of securities of the Company where, in any such case, the
holders of voting securities of the Company immediately prior to such
transaction or series of transactions own less than 50% of the voting securities
of the surviving or successor entity, or its parent, immediately following such
transaction or series of transactions; (ii) the sale of all or substantially all
of the Company's assets; or (iii) the sale of all or substantially all of the
capital stock or assets of RIH.

               1.3 "Good Reason" shall exist in the event that, other than under
circumstances involving Cause or the Executive's total disability (as defined
pursuant to the Company's long-term disability insurance plan covering the
Executive if any such plan is then in

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effect, or otherwise as determined by the Company's Board of Directors), the
Company, without the Executive's prior written consent; (i) materially alters or
reduces the Executive's duties, responsibilities and status with the Company
from those which exist as of the Effective Date of this Agreement; (ii) assigns
the Executive duties which are inconsistent with the Employee's position as
Senior Vice President of the Company and President of RIH; (iii) materially
breaches the terms of the Employment Agreement in respect to the payment of
compensation or benefits or in any other material respect and such breach is not
cured within ten days after notice thereof; (iv) requires the Employee, as a
condition to his continued employment, to be based more than 100 miles from the
location where he is based as of the Effective Date; or (v) requires the
Employee, as a condition to his continued employment, to perform illegal or
fraudulent acts or omissions.

        2. Retention and Severance Arrangement.

               2.1 Retention Bonus. In the event the Company effects a Change of
Control during the term of this Agreement, the Executive shall be entitled to
receive a cash bonus (the "Retention Bonus") in the amount of $350,000, payable
in a single lump sum promptly upon the fulfillment of the conditions set forth
in Section 2.2. The Executive may elect to reduce the Retention Bonus by an
amount that will reduce or eliminate any excise tax liability under Section 280G
of the Internal Revenue Code of 1986, as amended.

               2.2 Conditions to Receipt of Retention Bonus.

                      (a) In order for the Executive to be eligible to receive
the Retention Bonus, the following conditions must be met:

                             (i) The Executive must be continuously employed by
the Company on a full-time basis between the Effective Date of this Agreement
and the effective date of the Change of Control; and

                             (ii) Either of the following conditions must occur:
(A) the Executive remains continuously employed by the Company, RIH, the
acquiring entity or another subsidiary or affiliate of the acquiring entity
during the 12-month period following the effectiveness of the Change of Control;
or (B) prior to the end of such 12-month period, the Executive's employment by
one of such entities is terminated involuntarily by such entity other than for
Cause or voluntarily by the Executive with Good Reason.

               2.3 Reduction. The Retention Bonus payable to the Executive shall
not be reduced by any severance payments paid or payable to the Executive under
the terms of the Employment Agreement.

               2.4 Acceleration of Option Vesting. The option agreements between
the Company and the Executive shall be amended to provide that the vesting
provisions of all outstanding options to purchase the Company's Common Stock
held by the Executive shall be accelerated so that such options will vest and
become exercisable, in full, upon the Change of Control, to the extent any such
option agreements do not currently provide for such acceleration of vesting.

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               2.5 Annual Bonus. The Retention Bonus is not intended to replace
or reduce any bonus to which the Executive may be entitled under the Company's
existing annual incentive bonus program, which shall continue to be administered
in accordance with the Company's existing policies.

               2.6 Term. The term of this Agreement shall be twelve (12)
calendar months from the Effective Date of this Agreement.

        3. General

               3.1 Successors and Assigns. The provisions of this Agreement
shall inure to the benefit of and be binding upon the Company, the Executive and
each and all of their respective heirs, legal representatives, successors and
assigns. The duties, responsibilities and obligations of the Executive under
this Agreement shall be personal and not assignable or delegable by the
Executive in any manner whatsoever to any person, corporation, partnerships,
firm, company, joint venture or other entity. The Executive may not assign,
transfer, convey, mortgage, pledge or in any other manner encumber the
compensation or other benefits to be received by him or any rights which he may
have pursuant to the terms and provisions of this Agreement. The Company
covenants and agrees to require that any successor to the Company through a
Change of Control shall agree to honor the obligations of the Company under this
Agreement.

               3.2 Waiver. No waiver of any breach of any warranty,
representation, agreement, promise, covenant, paragraph, term or provision of
this Agreement shall be deemed to be a waiver of any preceding or succeeding
breach of the same or any other warranty, representation, agreement, promise,
covenant, paragraph, term or provision of this Agreement. No extension of the
time for the performance of any obligation or other act required or permitted by
this Agreement shall be deemed to be an extension of the time of the performance
of any other obligation or any other act required or permitted by this
Agreement.

               3.3 Entire Agreement. This Agreement, and the other agreements
referred to herein, including the Employment Agreement and the Company's benefit
plans, are the sole, complete and entire contract, agreement and understanding
between the Company and the Executive concerning the subject matter hereof.
Except as provided in the Employment Agreement or such benefit plans or as
otherwise provided herein, this Agreement supersedes any and all prior
contracts, agreements, plans, agreements in principle, correspondence, letters
of intent, understandings, and negotiations, whether oral or written, concerning
the subject matter hereof.

               3.4 Amendments. No amendment, modification, waiver, or consent
relating to this Agreement will be effective unless and until it is embodied in
a written document signed by the Company and by the Executive.

               3.5 Counterparts. The Agreement may be executed by the Company
and by the Executive in counterparts, each of which shall be deemed an original
and which together shall constitute one instrument.

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               3.6 Headings. The headings contained in this Agreement are for
reference purposes only and shall not in any manner whatsoever affect the
construction or interpretation of this Agreement or be deemed a part of this
Agreement for any purpose whatsoever.

               3.7 Severability. To the extent that any section, term,
provision, sentence, phrase, clause or word of this Agreement shall be found to
be illegal or unenforceable for any reason, such section, term, provision,
sentence, phrase, clause or word shall be modified or deleted in such a manner
as to make this Agreement, as so modified, legal and enforceable under
applicable laws. The remainder of this Agreement shall continue in full force
and effect.

               3.8 Applicable Law. This Agreement and each and every provision
of this Agreement shall be interpreted solely pursuant to the internal laws of
the State of California without regard to any conflicts of law principles
thereof.

               3.9 Construction. The language of this Agreement shall for all
purposes be construed as a whole, according to its fair meaning, not strictly
for or against the Executive or the Company, without regard to the identity or
status of any person or persons who drafted all or any portion of this
Agreement.

               3.10 Notices. Any notices to be given pursuant to this Agreement
by either party to the other party may be effected by personal delivery or by
registered or certified mail, postage prepaid with return receipt requested.
Mailed notices shall be addressed to the parties at the addresses stated below,
but each party may change its or his address by written notice to the other in
accordance with this Section 3.10. Notices delivered personally shall be deemed
received on the date of delivery. Notices delivered by mail shall be deemed
received on the third business day after the mailing thereof.

        Mailed notices to the Executive shall be addressed as follows:

               Swapan Sen
               63 Bunning Drive
               Voorkees, N.J. 08043

        Mailed notices to the Company shall be addressed as follows:

               Raytel Medical Corporation
               2755 Campus Drive, Suite 200
               San Mateo, California 94403-2515
               Attention:  Chief Executive Officer

               3.11 Arbitration. Any and all controversies, disputes and/or
claims in any manner arising out of or relating to this Agreement shall be
settled solely be arbitration in accordance with the Commercial Arbitration
Rules of the American Arbitration Association. Such arbitration proceeding shall
take place in the state and county of the Company's office where the Executive
is based. Judgment on any decision rendered by the arbitrator may be entered in
any court having jurisdiction thereof. Each party shall bear its own attorney's
fees and expenses and other costs in any arbitration proceeding. All
administrative fees and the fee of the

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arbitrator shall be borne by the parties equally. The arbitration provisions set
forth in this Section 3.11 are intended by the Executive and by the Company to
be absolutely exclusive for all purposes whatsoever, and applicable to each and
every controversy, dispute or claim in any manner arising out of or relating to
this Agreement, the meaning, application or interpretation of this Agreement,
any breach or claimed breach thereof or any voluntary or involuntary termination
of this Agreement with or without cause, including, without limitation, any such
controversy, dispute or claim which, if pursued through any state or federal
court or administrative agency, would arise at law, in equity or pursuant to
statutory, regulatory or common law rules, regardless of whether such dispute,
controversy or claim would arise in or from contract, tort or any other legal or
equitable theory or basis.

        IN WITNESS WHEREOF, the Company and the Executive have executed this
Agreement as of the date first set forth above.

RAYTEL MEDICAL CORPORATION

By:____________________________________     ___________________________________
   Richard F. Bader                         Swapan Sen
   Chairman and Chief Executive Officer

                                       5<PAGE>

                                                                    EXHIBIT 10.1

                                    AGREEMENT

                                JANUARY 28, 2002

                                 BY AND BETWEEN:

                             OZ COMMUNICATIONS, INC.

                                        &

                            ERICSSON RADIO SYSTEMS AB
                               ERICSSON TELECOM AB
                                  ERICSSON INC.
                              ERICSSON CANADA INC.*

* Certain portions of this exhibit have been omitted and filed separately with
  the Securities and Exchange Commission under an application for confidential
  treatment.

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                                    AGREEMENT

1       PARTIES

1.1     This Agreement ("Agreement") is made and entered into this 24th day of
        January 2002 by and between OZ Communications, Inc., a California
        corporation formerly known as OZ.COM, with its principal office at
        Snorrabraut 54, IS-105 Reykjavik, Iceland ("OZ") on the one hand, and
        Ericsson Radio Systems AB ("Ericsson Radio Systems"), registration
        number 556251-3258, a limited liability company duly incorporated under
        the laws of Sweden and having its principal place of business at
        Torshamnsgatan 23, SE-164 80 Stockholm, Sweden, Ericsson Telecom AB
        ("Ericsson Telecom"), registration number 556251-3258, a limited
        liability company duly incorporated under the laws of Sweden and having
        its principal place of business at Telefonplan, S-126 25 Stockholm,
        Sweden, Ericsson Inc., a Delaware corporation, and Ericsson Canada Inc.
        ("Ericsson Canada"), a Canada corporation having its principal place of
        business at 8400 Decarie Blvd., Town of Mount Royal, Quebec, Canada
        (Ericsson Radio Systems, Ericsson Telecom, Ericsson Inc. and Ericsson
        Canada sometimes collectively referred to as "Ericsson").

2       BACKGROUND AND INTENTIONS

2.1     OZ and Ericsson (the "Parties") have worked together since 1998 under
        the terms of certain agreements between them to develop, market and
        otherwise exploit the iPulse(TM) Software, a description of which is set
        forth as Exhibit A.

2.2     The Parties desire to terminate and supersede certain agreements more
        particularly specified in Section 3.

3       AGREEMENTS AMENDED OR TERMINATED BY THIS AGREEMENT

3.1     The Parties wish to modify their contractual relationship with respect
        to the following agreements:

        -  General Co-operation and Development Agreement made and entered into
           as of November 1, 2000 (the "GCDA"), by and between OZ and Ericsson
           Radio Systems.

        -  Hosted Service Agreement made and entered into as of July 19th, 2001
           ("Hosting Agreement"), by and between OZ and Ericsson Inc.

        -  iPulse Agency Agreement made and entered into as of November 1, 2000,
           by and between OZ and Ericsson Radio Systems.

                                       2
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        -  mPresence Agency Agreement made and between into as of November 1,
           2000, by and among OZ, Ericsson Radio Systems and certain
           shareholders of OZ.

        -  Shareholder Rights Agreement made and entered into as of February 4,
           1999, (the "Shareholder Rights Agreement") by and between OZ,
           Ericsson Inc and certain shareholders of OZ.

        -  Shareholder Rights Agreement made and entered into as of November 8,
           2000 (the "Shareholder Agreement"), by and between OZ, Ericsson
           Canada and certain shareholders of OZ.

        -  Specific Co-operation and Development Agreement for Communities and
           Link made and entered into as of February 4, 1999 (the "iPulse
           SCDA"), by and between OZ and Ericsson Telecom.

        -  Specific Co-operation and Development Agreement made and entered into
           as of November 8, 2000 (the "Canada SCDA"), by and between OZ and
           Ericsson Canada.

        -  Value Added Distribution and License Agreement, made and entered into
           as of November 1, 2000 (the "VADLA"), by and between OZ and Ericsson
           Radio Systems.

3.2     Except for the Shareholders Rights Agreement, which will be amended
        according to the agreement signed on December 20, 2001, the parties
        hereby terminate all of the agreements listed above.

4       iPULSE INTELLECTUAL PROPERTY RIGHTS

4.1     Ericsson herby irrevocably assigns to OZ an equal and undivided share of
        its right, title and interest in and to a) the iPulse(TM) Software,
        including source and object code, b) the "iPulse" trademark, with the
        limitation that Ericsson shall have the right to use iPulseTM as it has
        done before for any material it has in it possession the date of this
        agreement and c) hereby grant to OZ a worldwide and perpetual license
        for all purposes to all other intellectual property rights contained in
        and related to the iPulse(TM) software, including any Patent Rights,
        copyrights, rights to photographs, design rights, technical
        documentation and any other industrial and intellectual property rights
        contained in the source and object code, as set forth in Exhibit A.
        "Patent Rights" as used herein shall mean patents or patent applications
        relating to the iPulse(TM) software, in existence today, including, but
        not limited to the patents and patent applications of Appendix A of this
        Agreement, , and continuations-in-part and their counterparts in other
        countries, in whole or in part.

4.2     OZ shall as soon as reasonably possible but not later then March 30,
        return to Ericsson all Ericsson property including but not limited to
        all third-party develop

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        ment tools that Ericsson has previously made available to OZ for the
        development of the iPulse Software.

4.3     OZ and Ericsson shall each have the unrestricted and unlimited rights to
        exploit the iPulse(TM) software code and the iPulse Software in any way
        it sees fit, including but not limited to the rights to copy, modify,
        license, transfer rights to, use and distribute the iPulse(TM) software
        code.

4.4     Ericsson shall execute all papers, including patent applications,
        invention assignments, trademark and copyright assignments, and
        otherwise shall assist OZ as reasonably required to perfect in OZ the
        rights, title and other interests in iPulse(TM) expressly granted to OZ
        under this Agreement. Costs related to such assistance, if required,
        shall be paid by OZ.

5       UNCONDITIONAL PAYMENTS

5.1     In consideration for iPulse development services already provided by OZ
        to Ericsson up to the date hereof, which Ericsson has received and
        accepted, Ericsson agrees to pay OZ a final payment of US $6,000,000 on
        times as set forth below:

<TABLE>
<S>                                                 <C>
        -  Already received by OZ                   $   350,000

        -  On January 30, 2002                      $ 2,000,000

        -  On February 28, 2002                     $ 2,000,000

        -  On March 30, 2002                        $ 1,650,000
</TABLE>

5.2     The Parties agree that these payments and the services already rendered
        shall constitute the complete and final settlement of any claims or
        obligations between them and that would relate to any services performed
        under the agreements set forth in Section 3.

5.3     No royalties shall be payable by either Party to the other related to
        the sale or licensing of iPulse(TM) Software.

6       MISCELLANEOUS

6.1     Except for the fact that Ericsson no longer will offer iPulse to its
        customers, Ericsson and OZ agree not to communicate, internally within
        Ericsson, otherwise than on a need-to-know basis, or externally in press
        releases or by other means, the content of this Agreement without OZ's
        express consent in advance.

6.2     No announcement to news media pertaining to this Agreement shall be made
        until reviewed and approved by OZ and Ericsson. OZ has received the
        advice of counsel that the making of a public announcement and
        disclosure in United States Securities and Exchange Commission ("SEC")
        filings is necessary to comply with

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        the requirements of applicable laws and regulations and that, because of
        the materiality of the Ericsson relationship to OZ's shareholders, the
        SEC will deem this Agreement to be sufficiently material that no
        provision herein will be eligible for confidential treatment.

6.3     .  If any Party should default in the payment, when due, of any amount
        whatsoever due under this Agreement or under any of the agreements
        described in Section 5, the overdue amount shall bear interest at the
        prime rate of the bank of the Party to whom the obligation is due plus
        two percent (2%) per annum, calculated from the due date until full
        payment is made, without prejudice to the other rights of the Parties to
        this Agreement.

6.4     Neither Party shall be in default if failure to perform any obligation
        hereunder is caused solely by supervening conditions beyond that party's
        control, including acts of God, terrorism, civil commotion,
        telecommunications break down, strikes, labor disputes, and governmental
        demands or requirements.

6.5     If any legal action or other proceeding is brought with respect to the
        subject matter of this Agreement, its enforcement or as a result of a
        breach, default or misrepresentation in connection with any of the
        provisions of this Agreement, the successful or prevailing party shall
        be entitled to recover reasonable attorneys' fees and other costs
        incurred in such action or proceeding, in addition to any other relief
        to which such party may be entitled.

           OZ Communications Inc.

         By:  /s/ SKULI MOGENSEN
            -----------------------

         Title:     CEO
               --------------------

         Date:   28/01/02
              ---------------------

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           ERICSSON RADIO SYSTEMS AB           ERICSSON CANADA INC.,
                                                by power of attorney

         By: /s/ LARS BOMAN                 By:  /s/ LARS BOMAN
            -----------------------            -----------------------

         Title: VP & GM                     Title:  VP & GM
               --------------------               --------------------

         Date:  2002-02-11                  Date:  2002-02-11
              ---------------------              ---------------------

             ERICSSON TELECOM AB,                  ERICSSON INC.,
             by power of attorney               by power of attorney

         By: /s/ LARS BOMAN                 By: /s/ LARS BOMAN
            -----------------------            -----------------------

         Title:   VP & GM                   Title:  VP & GM
               --------------------               --------------------

         Date:  2002-02-11                  Date:  2002-02-11
              ---------------------              ---------------------

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<PAGE>

EXHIBIT A

The following is a list of all object code and documentation relative to iPulse,
but the iPulse Software as defined in the agreement shall only include the
portions of the below that are solely owned by Ericsson and developed by OZ for
Ericsson or solely developed by Ericsson within the iPulse development projects.
For the avoidance of doubt such iPulse Software does not include, a) any
Software developed by a third party for Ericsson, regardless of whether this
development was inside or outside the common development project with OZ, b) any
intellectual property rights owned by third parties or c) intellectual property
rights developed by Ericsson in any project outside the scope of the common
iPulse development projects with OZ, such as but not limited to IP Telephony
System, whether it is included in any object code or documentation set out in
the list below or not. Further for the avoidance of doubt, any subsidiary of OZ
is not regarded as a third party with respect to this Exhibit A.

[***]

*** These provisions consisting of 17 pages have been omitted and filed
separately under an application for confidential treatment.
<PAGE>

INTERVENTION

OZ.COM Canada Company, a Nova Scotia company with an office at Montreal, Canada,
intervenes in this Agreement, agreeing to be bound by it as a "Party and, for
greater certainty, agrees to the termination of the Canada SCDA, and
acknowledges the consideration granted by Ericsson under this Agreement
constitutes complete and final settlement of any claims or obligations that
OZ.COM Canada Company might have against Ericsson.

                                     OZ.COM Canada Company, by power of attorney

                                     By: /s/  SKULI MOGENSEN
                                        ----------------------------------------

                                     Title: CEO
                                     Date: 12-02-02

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