Document:

<PAGE>
                                                                   Exhibit 10.24

                                PROMISSORY NOTE
                            SECURED BY DEED OF TRUST

$1,000,000                                                     January    , 2001

                                                                    , California

     FOR VALUE RECEIVED, the undersigned, GILBERT C.P. HU ("Employee") and MAY
K.R. HU, husband and wife (jointly and severally, "Borrowers"), promise to pay
to the order of ALTIGEN COMMUNICATIONS, INC., a Delaware corporation ("Lender"),
at 47427 Fremont Boulevard, Fremont, California 94538 (or at such other place as
Lender may from time to time designate by written notice to Borrowers), in
lawful money of the United States, the principal sum of One Million One Dollars
($1,000,000).

     1. Payment: The principal and interest due pursuant to this Note shall be
paid as follows:

          (a) Upon the occurrence of a Maturity Event (as defined herein),
     Borrowers shall pay to Lenders all amounts due under this Note, including
     all unpaid principal and all accrued but unpaid interest on the principal
     amount hereof.

          (b) Principal and interest shall be payable in lawful money of the
     United States. Interest shall be calculated on the basis of a 360-day year
     consisting of twelve (12) months, each of thirty (30) days, and shall
     compound monthly. The interest accrued hereunder shall be due and payable
     in monthly installments on the last day of each month during the term of
     this Note. Each payment shall be applied first to accrued interest, then to
     any other amounts (other than principal) payable hereunder as designated by
     Lender, and then to reduce principal.

          (c) All payments made hereunder shall be made by Borrowers free and
     clear of, and without deduction for, any and all present and future taxes,
     levies, charges, deductions and withholdings. Borrowers shall pay upon
     demand any stamp or other taxes, levies or charges of any jurisdiction with
     respect to the execution, delivery, performance and enforcement of this
     Note.

     2. Security: This Note is secured by that certain Deed of Trust (the
"Second Deed of Trust") of even date herewith made by Borrowers, as trustors, to
First American Title Insurance Company, as trustee, for the benefit of Lender,
as beneficiary, which shall be recorded in the Official Records of the County of
Alameda, State of California, encumbering certain real property commonly known
as 603 Windmill Court, City of Fremont, County of Alameda, State of California
(the "Property"), described with particularity in the Second Deed of Trust,
which Borrowers shall occupy as their principal place of residence.

     3. Maturity Event: Upon the occurrence of a Maturity Event (as hereinafter
defined), the entire unpaid principal balance, together with all accrued but
unpaid interest thereon, and all other sums due hereunder, shall become
immediately due and payable without further demand or notice to Borrowers. To
the extent permitted by law, any of the following events shall be a "Maturity
Event" under this Note and the Second Deed of Trust:

<PAGE>
          (a) Borrowers shall fail to pay any amount of the principal or
     interest on this Note when due and shall fail to cure such non-payment
     within ten (10) days following written notice of such delinquency.

          (b) There shall occur any breach or default in the performance of any
     obligation of Borrowers or Employee contained in the promissory note
     payable by the Borrowers, as payors, to Bank of America, N.A., A D/B/A Of
     Nationsbank, N.A., as payee, in the original principal amount of Three
     Hundred Seventy Three Thousand Dollars ($373,000), executed in or about
     July, 1999, (the "Bank of America Note"), the deed of trust and or security
     and loan documents executed by Borrower in connection with the Bank of
     America Note (herein collectively with the Bank of America Note (the "First
     Loan Documents"); provided that such breach or default will not be deemed a
     Maturity Event if it is cured to the satisfaction of the holder of the note
     and the trustee of the deed of trust within any cure period expressly
     provided for in said First Loan Documents.

          (c) There shall occur a breach or default in the performance of any
     obligation of Borrowers or Employee contained in the Second Deed of Trust,
     as defined hereinbelow, or any other deed of trust or other security
     instrument now or hereafter encumbering the Property which may hereafter
     be executed by Borrowers for the purpose of securing this Note.

          (d) Borrowers, without the prior written consent of Lender,
     voluntarily or by operation of law, sell, convey, assign or otherwise
     transfer or agree to sell, convey or otherwise transfer, all or any portion
     of, or any interest in, the Property, provided, however, nothing herein or
     in the Second Deed of Trust or in the Loan Agreement shall make or be
     deemed to make Borrower's further encumbrance of the Property a Maturity
     Event or give Lender the right to accelerate the debt secured by the Second
     Deed of Trust as a consequence of such further encumbrance.

          (e) Borrowers (i) admit in writing their inability to pay debts, (ii)
     make an assignment for the benefit of creditors, (iii) file a voluntary
     petition in bankruptcy, effect a plan or other arrangement with creditors,
     liquidate their assets under arrangement with creditors, or liquidate their
     assets under court supervision, (iv) have an involuntary petition in
     bankruptcy filed against them that is not discharged within sixty (60) days
     after such petition is filed, or (v) apply for or permit the appointment of
     a receiver or trustee or custodian for any of their property or assets
     which shall not have been discharged within sixty (60) days after the date
     of appointment.

          (f) August 31, 2001.

          (g) The termination of Employee's employment with Lender for any
     reason, (other than the Employee's death).

          (h) Any representation or warranty of Employee or Borrowers contained
     herein, in any agreement entered into between Borrowers and Lender in
     connection herewith, or in any First Loan Document shall prove to be false
     or misleading in any material respect.

          (i) The Second Deed of Trust (as defined herein) is not recorded
     against the Property at the closing of the purchase by Borrower of the
     Property or at any time ceases to be a valid lien on the property subject
     only to the deed of trust securing the Bank of America Note.

          (j) One (1) year following the death of Employee.

                                      -2-

<PAGE>

        (k) Borrowers default in their obligation to pay any indebtedness or to
     perform any other obligation which is secured by a deed of trust or other
     lien on the Property or default under any deed of trust securing such
     indebtedness.

        (l) The amount of indebtedness secured by any interest in the Property
     superior in right to the Second Deed of Trust exceeds Three Hundred Seventy
     Three Thousand Dollars ($373,000).

     4. Interest: Interest shall accrue upon the outstanding principal balance
at the rate of Six and 88/100 percent (6.88%) per annum. Upon the failure of
Borrowers to pay the outstanding principal balance within thirty (30) days after
a Maturity Event, interest on the outstanding balance shall accrue thereafter at
the rate of twelve percent (12%) or if lower, the highest rate permitted by law.

     5. Late Charge: Because the actual damage to Lender resulting from any
default by Borrowers in the payment of any installment of principal and/or
interest when due is impractical and extremely difficult to ascertain, Lender
shall be entitled to recover six percent (6%) of the amount of any such
delinquent installment as liquidated damages if Borrowers fail to pay any
installment within ten (10) days after Borrower receives written notice from
Lender of the amount due and owing.

     6. Borrower's Representation: Borrowers hereby make the following
representations and warranties to the Lender and acknowledge that Lender is
relying on such representations in making the loan:

        (a) Borrowers shall have good and marketable title to the Property free
     and clear of any security interests, liens or encumbrances other than (i)
     the deed of trust in favor of Bank of America Mortgage Company, as
     beneficiary, securing the Bank of America Note, and (ii) the deed of trust
     in favor of Lender, securing this Note;

        (b) The consent of no other person or entity is required to grant to
     Lender the security interest in the Property evidenced by the Second Deed
     of Trust.

        (c) There are no actions, proceedings, claims or disputes pending or, to
     the Borrowers' knowledge, threatened against or affecting the Borrowers or
     the Property.

        (d) Borrowers have delivered to Lender true, correct and complete copies
     of all First Loan Documents.

     7. Borrowers' Additional Obligations: Borrowers shall take any and all
further actions that may from time to time be required to ensure that the Second
Deed of Trust creates a valid lien on the Property in favor of the Lender, which
shall secure the Note and be junior in priority only to the deed of trust
securing the Bank of America Note. Borrowers shall not modify, supplement, or
amend any First Loan Document without the prior written consent of the Company,
and in no event shall Borrowers cause or permit the principal indebtedness
payable under the First Loan Documents to exceed Three Hundred Seventy Three
Thousand Dollars ($373,000). Borrowers shall furnish evidence reasonably
satisfactory to the Lender that: (i) Borrowers have good and marketable title
to the Property; (ii) the consent of no other person or entity is required to
grant a security interest in the Property to the Lender; and (iii) there is no
other deed of trust, mortgage or

                                       -3-

<PAGE>

encumbrance against the Property other than the deed of trust securing the Bank
of America Note. If it should be hereafter determined that there are defects
against title or matters which could result in defects against title to the
Property, or that the consent of another person or entity is required to grant
to and perfect in the Lender a valid second-priority lien on the Property,
Borrowers shall promptly take all action necessary to remove such defects and to
obtain such consent and grant (or cause to be granted) and perfect such lien on
the Property. Failure of Borrowers to use all good faith to comply with the
provisions of this Paragraph or failure of the Second Deed of Trust to be a
valid lien against the Property, subject only to the lien of the deed of trust
securing the Bank of America Note shall be deemed a Maturity Event.

     8. Second Deed of Trust: As used herein, "Second Deed of Trust" shall mean
the deed of trust constituting a second-priority lien against the Property,
executed by Borrowers, as trustors, to First American Title Insurance Company,
as trustee, for the benefit of Lender, as beneficiary, to be recorded in the
Official Records of the County of Alameda, State of California. The Second Deed
of Trust provides, among other things, as follows:

        If the trustor shall sell, convey or alienate said property, or any part
     thereof, or any interest therein, or shall be divested of his title or any
     interest therein in any manner or way, whether voluntarily or
     involuntarily, without the written consent of the beneficiary being first
     had and obtained, beneficiary shall have the right, at its option, except
     as prohibited by law, to declare any indebtedness or obligations secured
     hereby, irrespective of the maturity date specified in any note evidencing
     the same, immediately due and payable.

        Notwithstanding the foregoing, nothing herein or in the Second Deed of
     Trust or in the Loan Agreement shall give Lender the right to accelerate
     the debt secured by the Second Deed of Trust upon Borrower's further
     encumbrance of the Property nor shall such further encumbrance constitute a
     default hereunder or thereunder.

     9. Notice: This Note is subject to Section 2924(i) and 2966 of the
California Civil Code which provides that the holder of this Note shall give
written notice to Borrowers or their successors-in-interest, of prescribed
information (as set forth in said Civil Code Sections) at least ninety (90) days
and not more than one hundred and fifty (150) days before any Balloon Payment is
due.

     10. Attorneys' Fees: In the event of Borrowers' default hereunder,
Borrowers shall pay all costs of collection, including reasonable attorney's
fees incurred by the holder hereof on account of such collection, whether or not
suit is filed hereon.

     11. Waiver: The waiver by Lender of any breach of or default under any
term, covenant or condition contained herein or in any other agreement referred
to above shall not be deemed to be a waiver of any subsequent breach of or
default under the same or any other such term, convenantor condition.

     12. No Usury: Borrowers hereby represent and warrant that at no time shall
the proceeds of the indebtedness evidenced hereby be used "primarily for
personal, family, or household purposes" as that term is defined and used in
Article XV of the California Constitution (as amended from time to time).
Anything in this Note to the contrary notwithstanding, it is expressly
stipulated

                                      -4-

<PAGE>
and agreed that the intent of Borrowers and Lender is to comply at all times
with all usury and other laws relating to this Note. If the laws of the State of
California would now or hereafter render usurious, or are revised, repealed or
judicially interpreted so as to render usurious, any amount called for under
this Note, or contracted for, charged or received with respect to the loan
evidenced by this Note, or if any prepayment by Borrowers results in Borrowers
having paid any interest in excess of that permitted by law, then it is
Borrowers' and Lender's express intent that all excess amounts theretofore
collected by Lender be credited to the principal balance of this Note (or, if
this Note has been paid in full, refunded to Borrowers), and the provisions of
this Note immediately be deemed reformed and the amounts therefor collectible
hereunder reduced, without the necessity of execution of any new document, so as
to comply with the then applicable law, but so as to permit the recovery of the
fullest amount otherwise called for hereunder.

     13. Prepayment: Borrowers may prepay all or any portion of this Note at any
time prior to the stated maturity date, with no premium or penalty, and interest
shall thereupon cease on the portion of the principal amount prepaid.

     14. General Provisions: This Note shall be governed by and construed in
accordance with the laws of the State of California. The makers of this Note
hereby waive presentment for payment, protest and demand, notice of protest,
demand and dishonor and nonpayment of this Note, and consent that Lender may
extend the time for payment or otherwise modify the terms of payment or any part
of the whole of the debt evidenced by this Note, at the request of any person
liable hereon, and such consent shall not alter nor diminish the liability of
any person. Borrowers hereby waive the defense of the statute of limitations in
any action on this Note to the extent permitted by law. Time is of the essence
of this Note, the Second Deed of Trust and any other document executed by
Borrowers in connection therewith. Liability hereunder shall be joint and
several both between Borrowers and among all other persons and entities now or
hereafter liable for all or any part of the Loan.

     15. No Covenant for Employment or Advances: Borrowers understand and
acknowledge that nothing herein shall modify Employee's at-will status at the
Company and does not constitute an employment agreement or a promise by the
Company to continue Employee's employment. Either the Company or Employee may
terminate such employment relationship at any time, with or without cause.

                                      -5-

<PAGE>
          16. THIS NOTE, THE LOAN AGREEMENT, THE DEED OF TRUST, AND ALL RELATED
     DOCUMENTATION ARE EXECUTED VOLUNTARILY AND WITHOUT ANY DURESS OR UNDUE
     INFLUENCE ON THE PART OF OR ON BEHALF OF THE PARTIES HERETO, WITH THE FULL
     INTENT OF CREATING THE OBLIGATIONS AND SECURITY INTERESTS DESCRIBED HEREIN
     AND THEREIN. THE PARTIES ACKNOWLEDGE THAT: (a) THEY HAVE READ SUCH
     DOCUMENTATION; (b) THEY HAVE BEEN REPRESENTED IN THE PREPARATION,
     NEGOTIATION AND EXECUTION OF SUCH DOCUMENTATION BY LEGAL COUNSEL OF THEIR
     OWN CHOICE; (c) THEY UNDERSTAND THE TERMS AND CONSEQUENCES OF THIS NOTE,
     THE LOAN AGREEMENT, THE DEED OF TRUST, AND ALL RELATED DOCUMENTATION AND
     THE OBLIGATIONS THEY CREATE; AND (d) THEY ARE FULLY AWARE OF THE LEGAL AND
     BINDING EFFECT OF THIS NOTE, THE DEED OF TRUST AND THE OTHER DOCUMENTS
     CONTEMPLATED BY THIS AGREEMENTS.

                            [Signatures on next page]

                                       -6-

<PAGE>

     IN WITNESS WHEREOF, Borrowers have executed this Note as of the day and
year first above written.

                                /s/ Gilbert C.P. Hu
                                ---------------------------------
                                GILBERT C.P. HU

                                /s/ May K.R. Hu
                                ---------------------------------
                                MAY K.R. HU

                                      -7-<PAGE>

                                                                   Exhibit 10.25

                         FIRST AMENDED PROMISSORY NOTE

$800,000.00                                                   September 17, 2001
                                                             Fremont, California

     FOR VALUED RECEIVED, the undersigned, GILBERT C.P. HU (the "Employee") and
MAY K.R. HU (jointly and severally, the "Borrowers"), promise to pay to ALTIGEN
COMMUNICATIONS, INC., a Delaware corporation ("Lender"), at 47427 Fremont
Boulevard, Fremont, California, 94538 (or at such other place as Lender may from
time to time designate by written notice to Borrower), in lawful money of the
United States, the principal sum of Eight Hundred Thousand Dollars
($800,000.00), on the following terms:

     1. Payment:

        On September 30, 2001, the principal amount of Four Hundred Thousand
Dollars ($400,000.00) and all accrued interest shall be immediately due and
payable in lawful money of the United States. On September 30, 2002, the
principal amount of Four Hundred Thousand Dollars ($400,000.00) and all accrued
interest shall be immediately due and payable in lawful money of the United
States.

     2. Security: This Note is secured by: 602,927 shares of Common Stock of
Lender (as adjusted for any stock splits, stock dividends, recapitalizations and
the like) (the "Stock") and Borrowers' brokerage accounts (the "Accounts") with
Charles Schwab & Co., Inc. and Salomon Smith Barney (the "Collateral"). The
value of the Collateral shall not be a limitation of the collection of the full
amount of this Note from Borrowers, it being the express intention of the
Borrowers that this be a "full recourse" note and obligation.

     3. Maturity Event: In addition to the stated maturity dates set forth in
Paragraph 1 of this Note, upon the occurrence of a Maturity Event (as
hereinafter defined), the entire principal amount of the Loan and any other sum
due hereunder, shall become immediately due and payable without further demand
or notice to Borrowers. To the extent permitted by law, any of the following
events shall be a "Maturity Event" under this Note and the Deed of Trust:

          (a) Thirty (30) days after the date of a voluntary termination or
cessation of Employee's employment with the Lender.

                                       1

<PAGE>

          (b) There shall occur any default in the performance of any obligation
of Borrowers contained in any deed of trust, security agreement or other
agreement (including any amendment, modification or extension thereof) which may
hereafter be executed by Borrowers for the purpose of securing this Note.

          (c) Borrowers (i) admit in writing inability to pay debts, (ii) make
an assignment for the benefit of creditors, (iii) file a voluntary petition in
bankruptcy, effect a plan or other arrangement with creditors, liquidate assets
under arrangement with creditors, or liquidate Borrowers' assets under court
supervision, (iv) have an involuntary petition in bankruptcy filed against him
or her that is not discharged within sixty (60) days after such petition is
filed, or (v) apply for or permit the appointment of a receiver or trustee or
custodian for any of Borrowers' property or assets which shall not have been
discharged within sixty (60) days after the date of appointment.

          (d) Any agreement or instrument executed in connection with this loan
proves to have been false or misleading.

          (e) Borrowers fail to execute, acknowledge and deliver the the
certificates evidencing the Stock or any other documents necessary to grant the
security interest in the Accounts concurrently with this Note.

          (f) Employee's death.

     4. Interest: Interest on the outstanding principal balance of this note
shall accrue at the rate of __________________________ (6.125%) per annum. Upon
the failure of Borrowers to pay the outstanding principal balance after a
Maturity Event, interest on the outstanding principal balance shall thereafter
accrue at the rate of seven and one-half percent (7.5%) per annum, or if lower,
the highest rate permitted by applicable law. Interest shall be calculated on
the basis of a three hundred sixty (360) day year consisting of twelve (12)
months, and shall compound annually.

     5. Borrower's Representations: Borrowers hereby make the following
representations and warranties to the Lender and acknowledges that Lender is
relying on such representations in making the loan:

          (a) Borrowers have not assigned, transferred any interest in, or
hypothecated any part of the Collateral.

          (b) The consent of no other person or entity is required to grant the
security interest in any part of the Collateral to the Lender.

                                        2

<PAGE>

        (c) There are no actions, proceedings, claims or disputes pending or, to
the Borrowers' actual knowledge threatened against or affecting the Borrowers,
or any part of the Collateral.

     6. Borrower's Additional Obligations: Employee shall (a) procure, execute
and deliver from time to time any endorsements, assignments, financing
statements and other documents, instruments and agreements and take other
actions reasonably deemed necessary or appropriate by the Lender to perfect,
maintain and protect its lien against the Collateral and the priority thereof;
(b) appear in and defend any action or proceeding which may affect its title to
or the Lender's interest in the Collateral; (c) not surrender or lose possession
of (other than to the Lender), sell, encumber, lease, rent, or otherwise dispose
of or transfer any part of the Collateral or proceeds thereof (until the payment
of the portion of such proceeds required to be paid to the Lender pursuant to
this Agreement has been made) or right or interest therein and to keep the
Collateral free of all liens, and (d) not take any action contrary the purposes
of this Note

     7. Attorneys' Fees: In the event of Borrowers' default hereunder, Borrowers
shall pay all costs of collection, including reasonable attorneys' fees incurred
by the holder hereof on account of such collection, whether or not suit is filed
hereon.

     8. Waiver: The waiver by Lender of any breach of or default under any term,
covenant or condition contained herein or in any other agreement referred to
above shall not be deemed to be a waiver of any subsequent breach of or default
under the same or any other such term, covenant or condition.

     9. No Usury: Anything in this Note to the contrary notwithstanding, it is
expressly stipulated and agreed that the intent of Borrowers and Lender is to
comply at all times with all usury and other laws relating to this Note. If the
laws of the State of California would now or hereafter render usurious, or are
revised, repealed or judicially interpreted so as to render usurious, any amount
called for under this Note, or contracted for, charged or received with respect
to the loan evidenced by this Note, or if any prepayment by Borrowers results in
Borrowers having paid any interest in excess of that permitted by law, then it
is Borrowers' and Lender's express intent that all excess amounts theretofore
collected by Lender be credited to the principal balance of this Note (or, if
this Note has been paid in full, refunded to Borrowers), and the provisions of
this Note immediately be deemed reformed and the amounts therefor collectible
hereunder reduced, without the necessity of execution of any new document, so as
to comply with the then applicable law, but so as to permit the recovery of the
fullest amount otherwise called for hereunder.

     10. Prepayment: Borrowers may prepay all or any portion of this Note at any
time prior to the stated maturity date, with no premium or penalty.

                                        3

<PAGE>

     11. Notice: This Note is subject to Section 2924(i) and 2966 of the
California Civil Code which provides that the holder of this Note shall give
written notice to Borrowers or their successors-in-interest, of prescribed
information (as set forth in said Civil Code Sections) as least ninety (90) days
and not more than one hundred and fifty (150) days before any Balloon Payment is
due.

     12. General Provisions: This Note shall be governed by and construed in
accordance with the laws of the State of California. Borrowers hereby waive
presentment for payment, protest and demand, notice of protest, demand and
dishonor and nonpayment of this Note, and consent that Lender may extend the
time for payment or otherwise modify the terms of payment or any part of the
whole of the debt evidenced by this Note, at the request of any person liable
hereon, and such consent shall not alter nor diminish the liability of any
person. Borrowers hereby waive the defense of the statute of limitations in any
action on this Note to the extent permitted by law.

     13. THIS NOTE, THE DEED OF TRUST AND ALL RELATED DOCUMENTATION ARE EXECUTED
VOLUNTARILY AND WITHOUT ANY DURESS OR UNDUE INFLUENCE ON THE PART OF OR ON
BEHALF OF THE PARTIES HERETO, WITH THE FULL INTENT OF CREATING THE OBLIGATIONS
AND SECURITY INTERESTS DESCRIBED HEREIN AND THEREIN. THE PARTIES ACKNOWLEDGE
THAT: (a) THEY HAVE READ SUCH DOCUMENTATION; (b) THEY HAVE BEEN REPRESENTED IN
THE PREPARATION, NEGOTIATION AND EXECUTION OF SUCH DOCUMENTATION BY LEGAL
COUNSEL OF THEIR OWN CHOICE OR THAT THEY HAVE VOLUNTARILY DECLINED TO SEEK SUCH
COUNSEL; (c) THEY UNDERSTAND THE TERMS AND CONSEQUENCES OF THIS NOTE, AND ALL
RELATED DOCUMENTATION AND THE OBLIGATIONS THEY CREATE; AND (d) THEY ARE FULLY
AWARE OF THE LEGAL AND BINDING EFFECT OF THIS NOTE, AND THE OTHER DOCUMENTS
CONTEMPLATED BY THIS AGREEMENT.

                                              AS BORROWERS:

                                              /s/ Gilbert C.P. Hu
                                              ---------------------
                                              Gilbert C.P. Hu

                                              /s/ May K.R. Hu
                                              ---------------------
                                              May K.R. Hu

                                        4

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