Document:

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                                                                    Exhibit-4.20

                                 KAZUHIRO ASANO
               3-10-22, Kitakokubu, Ichikawa-Shi, Chiba-ken, Japan

12 May 2005

Nam Tai Electronic & Electrical
Products Limited (the "Company")
15th Floor, China Merchants Tower,
Shun Tak Centre,
168-200 Connaught Road Central,
Hong Kong

Attn: Ms. Karene Wong, Chairman

Dear Sirs,

SUPPLEMENT LETTER REGARDING SERVICE -
NAMTEK SOFTWARE DEVELOPMENT COMPANY LIMITED
("NAMTEK", TOGETHER WITH ITS SUBSIDIARIES, THE "NAMTEK GROUP")

1.   I refer to the agreement relating to the sale and purchase of the entire
     issued share capital of Namtek dated 8 April 2005 between Nam Tai
     Electronics, Inc. and Asano Company Ltd. (as vendors) (the "VENDORS"), the
     Company (as purchaser) and the Vendors, Liu Xue Qing and myself (as
     warrantors) (the "AGREEMENT"). Unless redefined herein, terms used in this
     letter have the same meanings as defined in the Agreement.

2.   As one of the conditions to Completion under Clause 2.01(c) of the
     Agreement and in consideration of the Company entering into the Agreement,
     I hereby unconditionally and irrevocably undertake with the Company in
     terms as set out in the Schedule to this letter.

3.   Clause 8 (Announcements), Clause 10 (Further Assurance) and Clause 12
     (Notices) of the Agreement (mutatis mutandis) shall be incorporated in and
     be deemed to be part of this letter.

4.   I hereby confirm that this letter is entered into on a fair and equitable
     basis and voluntarily by myself in reliance of my own judgement and
     knowledge.

5.   This letter shall be governed by and construed in accordance with the laws
     of Hong Kong. I hereby submit to the exclusive jurisdiction of the courts
     of Hong Kong as regards any claim or matter arising under this letter.

6.   I hereby appoint Nam Tai Group Management Limited of 15th Floor China
     Merchants Tower, Shun Tak Centre, 168-200 Connaught Road Central, Hong Kong
     (or such other person, being resident or incorporated in Hong Kong, as I
     may by notice to the Company substitute) to accept service of all legal
     process arising out of or connected with this letter and service on Nam Tai
     Group Management Limited (or such substitute) shall be deemed to be service
     on myself.

Yours faithfully,
SIGNED SEALED and DELIVERED by  )
KAZUHIRO ASANO                  )
in the presence of:             )
                                )

<PAGE>

                                    SCHEDULE

                                  UNDERTAKINGS

1.   TERMINATION OF EMPLOYMENT WITH NAMTEK GROUP

1.01 I undertake with the Company that I will use my best endeavour to remain
     employed by a company within the Group or Namtek Group ("MY EMPLOYER", and
     such employment, "MY EMPLOYMENT"). If I terminate My Employment or My
     Employment is terminated for any reason other than those set out in
     paragraph 1.02 below (each a "TERMINATION EVENT") at any time before the
     third anniversary of the Completion Date, I shall pay to the Company, and
     the Company shall be entitled to recover from me, within 7 days from the
     date of the Termination Event, by way of liquidated damages, a compensation
     equal to my then income immediately preceding the termination of My
     Employment for the period commencing on the date of the Termination Event
     to the third anniversary of the Completion Date less any payment in lieu of
     notice which I have paid under My Employment ("COMPENSATION"). I
     acknowledge and agree that:

     (a)  the Compensation is a genuine pre-estimate of the loss that would be
          suffered by the Company as a result of the termination of My
          Employment on the date of the Termination Event, and is not a penalty;
          and

     (b)  the Company's right under this paragraph 1.01 to receive the
          Compensation is in addition to and without derogation from any rights
          that the Company may have against me at common law or in equity, which
          the Company reserves without limitation, including rights to seek
          injunctive relief or further damages.

1.02 Without prejudice to any other rights powers or remedies available to the
     Company under the Agreement or this letter or to My Employer and to the
     extent permitted by law, I shall not be required to pay to the Company the
     Compensation if My Employment is terminated (a) by reason of death, or (b)
     by reason of Ill Health, or (c) by My Employer in breach of the terms of My
     Employment, or (d) by My Employer (other than a termination without notice
     for cause). For the purpose of this paragraph 1.02,

     (i)  "ILL HEALTH" means such state of incapacity certified by a Registered
          Medical Practitioner that I am permanently unfit to perform the kind
          of work that I am performing under My Employment; and

     (ii) "REGISTERED MEDICAL PRACTITIONER" means any medical practitioner
          registered under the Medical Registration Ordinance (Cap. 161 of the
          laws of Hong Kong), or otherwise authorised and entitled to practise
          Western medicine in Japan in accordance with the laws of Japan.

2.   CONFIDENTIALITY UNDERTAKING

2.01 I shall neither during My Employment (except in the proper performance of
     my duties) nor at any time (without limit) after the termination of My
     Employment (howsoever the same is determined and whether in breach of
     contract or otherwise):

     (a)  divulge or communicate to any person, firm, company, business entity
          or other organisation;

<PAGE>

     (b)  use for my own purposes or for any purposes other than those of any
          company in the Group or Namtek Group; or

     (c)  through any failure to exercise due care and diligence, cause any
          unauthorised disclosure of

     any Confidential Information relating to NTE Inc. or any of its
     subsidiaries ("NAM TAI GROUP", which includes the Group and Namtek Group).

2.02 "CONFIDENTIAL INFORMATION" shall include, in relation to the Company and/or
     Nam Tai Group:

     (a)  all business confidential and/or secret information,

     (b)  all technical information and rights,

     (c)  trade secrets,

     (d)  confidential operations and processes,

     (e)  dealings with customers or suppliers,

     (f)  inventions, designs, copyrights, know-how, formulae, product lines,

     (g)  marketing plans and sales forecasts,

     (h)  financial information results and forecasts and research activities,

     (i)  details of employees and officers and of the remuneration and other
          benefits paid to them,

     (j)  any other information concerning Nam Tai Group,

     (k)  information relating to the Company's and/or Nam Tai Group's business,
          finance, transactions, trade connections, suppliers, customers,
          agents, distributors and their terms of business or requirements,

     (l)  any information which has been given to any member of Nam Tai Group in
          confidence by any customer, supplier or other person, whether written
          or non-written,

     but shall not include information that:

     (m)  was rightfully in my possession and not subject to an obligation of
          confidentiality on me before the negotiations leading to the
          commencement of My Employment, or

     (n)  is or, after the date of the letter to which this Schedule is
          appended, becomes available in the public domain (other than as a
          result of a breach of the letter or this Schedule).

2.03 All notes, memoranda, records, lists of customers and suppliers and
     employees, correspondence, documents, computer and other discs and tapes,
     data listings, codes, designs and drawings and other documents and material
     whatsoever (whether made or

<PAGE>

     created by me or otherwise) relating to the business of any member of Nam
     Tai Group (and any copies of the same):

     (a)  shall be and remain the property of the relevant company in Nam Tai
          Group; and

     (b)  shall be handed over by myself to the relevant company in Nam Tai
          Group on demand and in any event on the termination of My Employment.

2.04 Without prejudice to paragraph 2.05, if I fail to comply with any provision
     of this paragraph 2, I shall indemnify the Company of all losses costs and
     expenses incurred by the Company in relation to its investment in Namtek
     Group or otherwise by Nam Tai Group as a result of a breach of my
     undertaking under this paragraph 2. Such indemnity payment shall in any
     event be made not more than 7 days after the date on which the Company
     notifies me of the amount of its costs and expenses to be reimbursed by me
     hereunder. I acknowledge and agree that:

     (a)  any written notice from the Company from time to time specifying the
          indemnity payment under this paragraph 2.04 shall be final, conclusive
          and binding on me in the absence of manifest error;

     (b)  to the extent not prohibited by law, the Company may deduct from any
          sums payable to me by the Company (howsoever due or payable) any part
          of the indemnity payment under this paragraph 2.04 at that time due
          and owing by me to the Company;

     I also acknowledge and undertake that I shall immediately indemnify the
     Company against any loss, cost, damage or expense (including any legal
     fees) that the Company may incur as a result of my failure to comply with
     any aspect of this paragraph 2.04.

2.05 I acknowledge that monetary damages would not be an adequate remedy for the
     Company for breach by myself of my undertakings under this paragraph. I
     agree that the Company shall be entitled to specific performance of my
     obligations in this paragraph and to injunctive and other equitable relief
     in addition to any other remedy to which it may be entitled at law or in
     equity.

3.   NON-COMPETITION AND NON-SOLICITATION UNDERTAKINGS

3.01 I acknowledge that:

     (1)  in the course of My Employment, I will or may have dealings with
          clients and fellow employees over whom I may develop a degree of
          influence;

     (2)  the Nam Tai Group invests a considerable amount of time, energy and
          money in training its employees and that those employees and the
          general stability of the workforce form an important part of the
          goodwill of the Nam Tai Group;

     (3)  in the course of My Employment, I will have access to and be entrusted
          with confidential information in respect of the Nam Tai Group, its
          clients and their respective business.

     In order to safeguard the Nam Tai Group's clientele, goodwill and name and
     to protect the Nam Tak Group's legitimate proprietary interests, I covenant
     that I will not without the prior written consent of the Company (such
     consent to be withheld only in so far as

<PAGE>

     may be reasonably necessary to protect the legitimate interests of the Nam
     Tai Group) during the currency of My Employment and for a period of 6
     months after the termination of My Employment for whatever reason (other
     than a termination by the Company in breach of the terms of My Employment):

     (a)  be engaged or interested (whether as a director, shareholder,
          principal, consultant, agent, partner or employee) in any business
          concern (of whatever kind) which shall in Hong Kong PRC and Japan be
          in competition with any company in the Nam Tai Group in the provision
          of services or the manufacture, sale or supply of goods, being
          services or goods of a kind with which I was concerned to a material
          extent during the period of 12 months prior to the termination of My
          Employment, provided always that nothing in this paragraph 3.01 shall
          restrain me from engaging or being interested as aforesaid in any such
          business concern in so far as my duties or work relate principally to
          services or goods of a kind with which I was not concerned during the
          period of 12 months prior to the termination of My Employment;

     (b)  either on my own behalf or on behalf of any other person, firm,
          company or organisation in respect of any services of a kind provided
          or any goods of a kind manufactured sold or supplied by any company in
          the Nam Tai Group in respect of the provision or sale or supply of
          which I may have been engaged during My Employment:

          (i)  canvass, solicit or approach or cause to be canvassed, solicited
               or approached for orders or with a view to providing services
               thereto; or

          (ii) directly or indirectly deal with any person, firm, company or
               organisation who at the date of the termination of My Employment
               or within 12 months prior to such date is or was a client or
               customer of any company in the Nam Tai Group or was in the habit
               of dealing under contract with any company in the Nam Tai Group
               or in the process of negotiating with any company in the Nam Tai
               Group and with whom or which I had dealings during the said
               period; or

          (iii) interfere or seek to interfere with the continuance of supplies
               to any company in the Nam Tai Group (or the terms relating to
               such supplies) from any suppliers who have been supplying goods,
               materials or services to any company in the Nam Tai Group at any
               time during the last 12 months of My Employment and with whom or
               which I had dealings during the said period; and

     (c)  either on my own behalf or on behalf of any other person, firm,
          company or organisation:

          (i)  directly or indirectly solicit or entice or endeavour to solicit
               or entice away from any company in the Nam Tai Group any
               director, employee or executive of managerial status engaged in
               its or their business and with whom I had dealings at any time
               during the last 12 months of My Employment; or

          (ii) directly or indirectly solicit or entice or endeavour to solicit
               or entice away from any company in the Nam Tai Group any person
               employed or engaged by it who by reason of such employment or
               engagement is or is reasonably likely to be in possession of any
               confidential information or trade secrets relating to the
               business of any company in

<PAGE>

               the Nam Tai Group or the business of the customers of any company
               in the Nam Tai Group and with whom I had dealings at any time
               during the last 12 months of My Employment.

3.02 While the restrictions contained in paragraphs 2 and 3 (on which I have had
     the opportunity to take independent advice) are considered by the Company
     and myself to be reasonable in all the circumstances, it is agreed that if
     any such restrictions, by themselves or taken together, shall be adjudged
     to be void as going beyond what is reasonable in all the circumstances for
     the protection of the interests of the Company or any other company in Nam
     Tai Group but would be adjudged reasonable if part or parts of the wording
     thereof were deleted, the relevant restriction or restrictions shall apply
     with such deletion(s) as may be necessary to make it or them valid and
     effective.

4.   INVENTIONS AND OTHER INTELLECTUAL PROPERTY RIGHTS

4.01 In connection with any inventions or other intellectual property made or
     created by myself in the course of my duties under My Employment, I agree
     and acknowledge that I have a special responsibility to further the
     interests of Nam Tai Group.

4.02 Any invention or improvement or design made or process or information
     discovered or copyright work or trade mark or trade name or get-up created
     by myself during the course of My Employment (whether capable of being
     patented or registered or not and whether or not made or discovered in the
     course of My Employment) in conjunction with or in any way affecting or
     relating to the business of any member of Nam Tai Group or capable of being
     used or adapted for use therein or in connection therewith shall
     irrespective of any termination of my employment forthwith be disclosed to
     the Company and shall belong to and be the absolute property of such member
     of Nam Tai Group as the Company may direct.

4.03 I, if and whenever required so to do by the Company, shall at the expense
     of a member of Nam Tai Group, apply or join with such company in applying
     for letters patent or other protection or registration for any such
     invention, improvement, design, process, information, work, trade mark,
     trade name or get-up as aforesaid which belongs to such company and shall
     at the expense of such company execute and do all instruments and things
     necessary for vesting the said letters patent or other protection or
     registration when obtained and all rights, title and interest to and in the
     same in such company absolutely and as sole beneficial owner or in such
     other person as the Company may specify.

4.04 I hereby irrevocably appoint the Company to be my attorney in my name and
     on my behalf to execute and do any such instrument or thing and generally
     to use my name for the purpose of giving to the Company the full benefit of
     this paragraph and in favour of any third party a certificate in writing
     signed by any director or by the secretary of the Company that any
     instrument or act falls within the authority hereby conferred shall be
     conclusive evidence that such is the case.

5.   GENERAL

5.01 I shall abide by the provisions of the employee's handbook (or its
     equivalents), policies and guidelines issued and modified by Nam Tai Group
     (including the Group and Namtek Group) from time to time.

<PAGE>

5.02 Paragraphs 2, 3 and 4 above and this paragraph 5.02 and paragraph 5.03
     shall survive the termination of My Employment.

5.03 If any clause in this letter is adjudged to be void but would be
     enforceable if part or parts of the wording thereof were deleted, the
     relevant clause shall be adjusted accordingly to the extent necessary to
     make it valid and enforceable.<PAGE>
                                                                    Exhibit-4.21

Commercial Banking - GP 2, Division A
(CARM 050728)

PRIVATE AND CONFIDENTIAL

Nam Tai Electronics Inc
15/F China Merchants Tower
Shun Tak Centre
168-200 Connaught Road Central
Hong Kong                                                       9 September 2005

Attn : Mr Joseph Li

Dear Sir

BANKING FACILITIES
NAM TAI ELECTRONICS INC (A/C NO. 500-401898) - NEW BORROWER
NAM TAI GROUP MANAGEMENT LTD (A/C NO. 500-815287) - no longer be a borrower

With reference to our recent discussion, we are pleased to advise that we have
reviewed your banking facilities and offer a renewal within the following
revised limits which will be made available on the specific terms and conditions
outlined herein and subject to the satisfactory completion of the security
detailed below. These facilities are subject to review at any time and, in any
event by 31 May 2006, and also subject to our overriding right of suspension,
withdrawal and repayment on demand, including the right to call for cash cover
on demand for prospective and contingent liabilities.

<TABLE>
<CAPTION>
                                                              New              Previously
                                                       -----------------   -----------------
<S>                                                    <C>                 <C>
FACILITIES AVAILABLE TO NAM TAI GROUP MANAGEMENT LTD
Overdraft                                                     NIL          HKD500,000.-
Treasury Facilities                                           NIL          USD30,000,000.-
   within which (1) Foreign Exchange                          NIL          (USD30,000,000.-)
                (2) Currency Option                           NIL          (USD30,000,000.-)
Corporate Card                                                NIL          HKD1,100,000.-

FACILITIES AVAILABLE TO NAM TAI ELECTRONICS INC
Overdraft                                                 HKD500,000.-     NIL
</TABLE>

Interest on the overdraft facility will be
charged on daily balances at our HKD best
lending rate, which is currently 6.75% per
annum, but subject to fluctuation at our
discretion and payable monthly in arrears to
the debit of your current account.

                                                                     Page 1 of 3

THE HONGKONG AND SHANGHAI BANKING CORPORATION LIMITED
HSBC Main Building, 1 Queen's Road Central, Hong Kong
Tel: (852) 2822 1111 Fax: (852) 2351 4230
Telex: 73205 HSBC HX Telegrams: Hongbank Hongkong
Web: www.hsbc.com.hk

Incorporated in the Hong Kong SAR with limited liability
Registered at the Hong Kong Companies Registry No. 263876

<PAGE>
Nam Tai Electronics Inc                                         9 September 2005

<TABLE>
<CAPTION>
                                                         New              Previously
                                                  -----------------   -----------------
<S>                                               <C>                 <C>
Treasury Facilities                                USD30,000,000.-    NIL

   within which:

   Foreign Exchange:                              (USD30,000,000.-)   NIL

   -    For booking forward exchange
        contracts with individual contracts
        up to a maximum of 6 months'
        duration.

   Currency Option:                               (USD30,000,000.-)   NIL

   -    maximum maturity : up to a maximum of
        6 months forward for buying in option
        only
</TABLE>

Terms and Conditions

Contracts for treasury products may only be entered into under these facilities
to cover exchange rate exposure incurred in the normal course of your business.

All treasury product facilities remain subject to our overriding right to call
for cash cover on demand if in the Bank's view your mark-to-market position with
us requires such cover. Further, the Bank may, after having made reasonable
attempts to discuss the position with yourselves, close out any or all of your
outstanding treasury products contracts and demand settlement of the balance
due.

All spot and forward foreign exchange transactions and all currency option
transactions shall be subject to the terms of a Master Agreement in form
published by the International Swaps and Derivatives Association ("ISDA").

<Table>
<S>                                               <C>                  <C>
Commercial Card Facility                          HKD1,100,000.-       NIL

Commercial Cards approved by us and to be
issued to your executives.

The terms and conditions governing the
Commercial Card Facility are detailed in our
HSBC Commercial Card Employer's Participation
Agreement to be signed by you.
</Table>

Default Interest

Please note that interest will be payable on sums which are overdue, drawings
which are in excess of agreed limits and amounts demanded and not paid, at the
maximum rate stipulated in the Bank's Tariff which is accessible at
http://www.hsbc.com.hk/hk/commercial/tool/pdf/c_tariff.pdf. The Bank will
provide you with a hard copy of the Tariff at your request. Interest at the
applicable rate will be payable monthly in arrears to the debit of your current
account.

Accrual of Interest and Other Sums

Please note that interest and other sums expressed to be chargeable or payable
on a periodic basis will nonetheless accrue from day to day and amounts so
accrued may be demanded at any time.

                                                                     Page 2 of 3

<PAGE>
Nam Tai Electronics Inc                                         9 September 2005

Upon acceptance the facility letter, we shall release the existing Unlimited
Corporate Guarantee dated 26 April 2001 from Nam Tai Electronics Inc (covering
facilities to Nam Tai Group Management Ltd), which will be cancelled after a
retention period considered by us to be reasonably appropriate, which is
normally 6 months.

Please note that all costs and expenses (including legal fees) incurred by us in
connection with the extension of these facilities and any matters arising are to
be reimbursed by you on demand.

This facility letter shall be governed by and construed in accordance with the
laws of Hong Kong Special Administrative Region ("Hong Kong"). The parties
hereby submit to the non-exclusive jurisdiction of the courts of Hong Kong.

Please arrange for the AUTHORISED SIGNATORIES OF NAM TAI ELECTRONICS INC AND NAM
TAI GROUP MANAGEMENT LTD, in accordance with the terms of the mandates given to
the bank, to sign and return to us the duplicate copy of this letter to signify
your understanding and acceptance of the terms and conditions under which these
revised facilities are granted.

Unless expressed in writing from Nam Tai Electronics Inc and Nam Tai Group
Management Ltd to the contrary, we may provide any information relating to any
of your accounts with us and any facilities we may provide to you from time to
time or their conduct or any other information concerning your relationship with
us to any other company or office which at the relevant time belongs to or is
part of the HSBC Group.

Section 83 of the Banking Ordinance

Please note that Section 83 of the Banking Ordinance has imposed on us as a bank
certain limitations on advances to persons related to our directors or
employees. In acknowledging this facility letter you should advise us whether
you are in any way related to any of our directors or employees within the
meaning of Section 83 and in the absence of such advice we will assume that you
are not so related. We would also ask, should you become so related subsequent
to acknowledging this facility letter, that you immediately advise us in
writing.

These revised facilities will remain open for acceptance until the close of
business on 29 September 2005 and if not accepted by that date will be deemed to
have lapsed.

We are pleased to be of continued assistance.

Yours faithfully

Peter Choi
Senior Vice President

Encl.

/ml

                                                                     Page 3 of 3

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