EXHIBIT 4.2.1

      NEITHER THESE SECURITIES NOR THE SECURITIES ISSUABLE UPON CONVERSION
      HEREOF HAVE BEEN REGISTERED WITH THE UNITED STATES SECURITIES AND EXCHANGE
      COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE OR UNDER THE
      SECURITIES ACT OF 1933, AS AMENDED. THE SECURITIES ARE RESTRICTED AND MAY
      NOT BE OFFERED, RESOLD, PLEDGED OR TRANSFERRED EXCEPT AS PERMITTED UNDER
      THE ACT PURSUANT TO REGISTRATION OR EXEMPTION OR SAFE HARBOR THEREFROM.

No.   00-                                                   US $
      -------------

                               AMBIENT CORPORATION

                 10% CONVERTIBLE DEBENTURE DUE FEBRUARY 28, 2002

      THIS DEBENTURE is one of a duly authorized issue of up to $2,000,000 in
Debentures of AMBIENT CORPORATION, a corporation organized and existing under
the laws of the State of Delaware (the "Company") designated as its 10%
Convertible Debentures. Such Debentures may be issued in series, each of which
may have a different maturity date, but which otherwise have substantially
similar terms.

      FOR VALUE RECEIVED, the Company promises to pay to ____________________,
the registered holder hereof (the "Holder"), the principal sum of
_________________________ Dollars (US $__________) on February 28, 2002 (the
"Maturity Date") and to pay interest on the principal sum outstanding from time
to time in arrears (i) prior to the Maturity Date, quarterly, on the last day of
March, June, September and December of each year, (ii) upon conversion as
provided herein or (iii) on the Maturity Date, at the rate of 10% per annum
accruing from February 17, 2000, the date of initial issuance of this Debenture.
Accrual of interest shall commence on the first such business day to occur after
the date hereof and shall continue to accrue on a daily basis until payment in
full of the principal sum has been made or duly provided for.

      This Debenture is subject to the following additional provisions:

      1. The Debentures are issuable in denominations of Twenty-five Thousand
Dollars (US$25,000) and integral multiples thereof. The Debentures are
exchangeable for an equal aggregate principal amount of Debentures of different
authorized denominations, as requested by the Holder surrendering the same. No
service charge will be made for such registration or transfer or exchange.

      2. The Company shall be entitled to withhold from all payments of
principal of, and interest on, this Debenture any amounts required to be
withheld under the applicable provisions of


                                       1
<PAGE>

the United States income tax laws or other applicable laws at the time of such
payments, and Holder shall execute and deliver all required documentation in
connection therewith.

      3. This Debenture has been issued subject to investment representations of
the original purchaser hereof and may be transferred or exchanged only in
compliance with the Securities Act of 1933, as amended (the "Act"), and other
applicable state and foreign securities laws. In the event of any proposed
transfer of this Debenture, the Company may require, prior to issuance of a new
Debenture in the name of such other person, that it receive reasonable transfer
documentation including legal opinions that the issuance of the Debenture in
such other name does not and will not cause a violation of the Act or any
applicable state or foreign securities laws. Prior to due presentment for
transfer of this Debenture, the Company and any agent of the Company may treat
the person in whose name this Debenture is duly registered on the Company's
Debenture Register as the owner hereof for the purpose of receiving payment as
herein provided and for all other purposes, whether or not this Debenture be
overdue, and neither the Company nor any such agent shall be affected by notice
to the contrary.

      4. A. The Holder of this Debenture is entitled, at its option, subject to
the following provisions of this Section 4, to convert all or a portion of this
Debenture into shares of Common Stock of the Company, $.001 par value per share
("Common Stock") of the Company at any time until the Maturity Date (except as
contemplated by Section 5 hereof), at a conversion price for each share of
Common Stock equal to Forty Cents ($0.40) (the "Conversion Rate"; which amount
is subject to adjustment as hereinafter provided); provided that the principal
amount being converted is the lower of (x) at least Twenty-five Thousand Dollars
[US $25,000] (unless if at the time of such election to convert the aggregate
principal amount of all Debentures registered to the Holder is less than
Twenty-five Thousand Dollars [US $25,000], then the whole amount thereof) or (y)
the maximum amount which the Holder can then convert pursuant to the terms of
Section 4(D) hereof.

            B. Conversion shall be effectuated by surrendering the Debentures to
be converted to the Company or to the Company's transfer agent, North American
Transfer Company, accompanied by or preceded by facsimile or other delivery to
the Company of the form of conversion notice attached hereto as Exhibit A,
executed by the Holder of the Debenture evidencing such Holder's intention to
convert this Debenture or a specified portion hereof, and accompanied, if
required by the Company, by proper assignment hereof in blank. Subject to the
provisions of Section 4(D) hereof, interest accrued or accruing from the date of
issuance to the date of conversion shall, at the option of the Company, be paid
in cash or Common Stock upon conversion at the Conversion Rate applicable to
such conversion. No fractional shares of Common Stock or scrip representing
fractions of shares will be issued on conversion, but the number of shares
issuable shall be rounded to the nearest whole share. The date on which notice
of conversion is given (the "Conversion Date") shall be deemed to be the date on
which the Holder faxes or otherwise delivers the conversion notice ("Notice of
Conversion"), substantially in the form annexed hereto as Exhibit A, duly
executed, to the Company, provided that the Holder shall deliver to the
Company's transfer agent or the Company the original Debentures being converted
within five (5) business days thereafter (and if not so delivered with such
time, the Conversion Date shall be the date on which


                                       2
<PAGE>

the later of the Notice of Conversion and the original Debentures being
converted is received by the Company). Facsimile delivery of the Notice of
Conversion shall be accepted by the Company at facsimile number (0119722)
648-2997; ATTN: Aryeh Weinberg. Certificates representing Common Stock upon
conversion will be delivered within three (3) business days if the address for
delivery is in the United States (and within eight (8) business days if the
address for delivery is outside the United States) from the date later of the
Notice of Conversion is delivered to the Company as contemplated in the first
sentence of this paragraph C or the original Debenture is delivered to the
Company's transfer agent or to the Company.

            C. Anything herein to the contrary notwithstanding, in the event the
Company breaches the provisions of Section 4(g) of the Securities Purchase
Agreement, the Conversion Rate shall be amended to be equal to (i) 90% of (ii)
the Conversion Rate determined in accordance with the other provisions of this
Debenture without regard to this Section 4(C), and the Holder may require the
Company to immediately redeem the outstanding portion of this Debenture in
accordance with clause (y) of Section 6 hereof.

            D. Notwithstanding any other provision hereof, of the Warrants or of
any of the other Transaction Agreements (as those terms are defined in the
Securities Purchase Agreement), in no event (except (i) with respect to an
automatic conversion, if any, of a Debenture as provided in the Debentures or a
conversion pursuant to a Redemption Notice Conversion [as defined below], (ii)
as specifically provided in this Debenture as an exception to this provision, or
(iii) while there is outstanding a tender offer for any or all of the shares of
the Company's Common Stock) shall the Holder be entitled to convert any
Debenture, or shall the Company have the obligation to convert all or any
portion of this Debenture (and the Company shall not have the right to pay
interest on this Debenture), to the extent that, after such conversion, the sum
of (1) the number of shares of Common Stock beneficially owned by the Holder and
its affiliates (other than shares of Common Stock which may be deemed
beneficially owned through the ownership of the unconverted portion of the
Debentures or unexercised portion of the Warrants), and (2) the number of shares
of Common Stock issuable upon the conversion of the Debentures with respect to
which the determination of this proviso is being made, would result in
beneficial ownership by the Holder and its affiliates of more than 9.99% of the
outstanding shares of Common Stock (after taking into account the shares to be
issued to the Holder upon such conversion). For purposes of the proviso to the
immediately preceding sentence, beneficial ownership shall be determined in
accordance with Section 13(d) of the Securities Exchange Act of 1934, as amended
(the "1934 Act"), except as otherwise provided in clause (1) of such sentence.
The Holder, by its acceptance of this Debenture, further agrees that if the
Holder transfers or assigns any of the Debentures to a party who or which would
not be considered such an affiliate, such assignment shall be made subject to
the transferee's or assignee's specific agreement to be bound by the provisions
of this Section 4(D) as if such transferee or assignee were the original Holder
hereof.

      5. A. (i) Notwithstanding any other provision hereof to the contrary, at
any time prior to the Conversion Date, the Company shall have the right to
redeem all or any portion of the then outstanding principal amount of the
Debentures then held by the Holder in cash for an amount (the


                                       3
<PAGE>

"Redemption Amount") equal to the sum of (a) such outstanding principal of the
Debentures plus all accrued but unpaid interest thereon through the date the
Redemption Amount is paid to the Holder (the "Redemption Payment Date"), plus
(b) the Redemption Premium (as defined below).

            (ii) The "Redemption Premium" shall be an amount equal to the
excess, if any, of (a) an amount equal to (I) the number of shares of Common
Stock into which the Holder could have converted the Debentures being redeemed
had the Holder effected such conversion on the Redemption Payment Date,
multiplied by (II) the closing transaction sale price of the Common Stock on the
trading day immediately preceding the Redemption Payment, over (b) the principal
of the Debentures so redeemed.

            (iii) The Company shall give at least ten (10) business days'
written notice of such redemption to the Holder (the "Notice of Redemption").
The date so specified in such Notice of Redemption shall be the Redemption
Payment Date. Anything in the preceding provisions of this Section 5 to the
contrary notwithstanding, the Redemption Amount shall, unless otherwise agreed
to in writing by the Holder after receiving the Notice of Redemption, be paid to
the Holder in good funds at least five (5) but not more than ten (10) business
days from the date of the Notice of Redemption, except that, with respect to any
Debentures for which a Notice of Redemption is given, the Holder shall have the
right, exercisable by giving a Notice of Conversion is submitted to the Company
within five (5) business days of the Holder's receipt of the Company's Notice of
Redemption, to convert any or all of the Debentures sought to be redeemed (a
"Redemption Notice Conversion") and the Redemption Notice Conversion shall take
precedence over the redemption contemplated by the Notice of Redemption. Such
Debentures shall be converted in accordance with the terms hereof. Furthermore,
in the event such Redemption Amount is not timely made, any rights of the
Company to redeem outstanding Debentures shall terminate, and the Notice of
Redemption shall be null and void. Any redemption contemplated by this Debenture
shall be made only in cash by the payment of immediately available good funds to
the Holder.

            B. Any Debentures not previously converted as of the Maturity Date,
shall be deemed to be automatically converted, without further action of any
kind by the Company or any of its agents, employees or representatives, as of
the Maturity Date at the Conversion Rate applicable on the Maturity Date
("Mandatory Conversion").

      6. The Holder recognizes that the Company may be limited in the number of
shares of Common Stock it may issue by (i) reason of its authorized shares, or
(ii) the applicable rules and regulations of the principal securities market on
which the Common Stock is listed or traded (collectively, the"Cap Regulations").
Without limiting the other provisions hereof, (i) the Company will take all
steps reasonably necessary to be in a position to issue shares of Common Stock
on conversion of the Debentures without violating the Cap Regulations and (ii)
if, despite taking such steps, the Company still can not issue such shares of
Common Stock without violating the Cap Regulations, the Holder of this Debenture
(to the extent the same can not be converted in compliance with the Cap
Regulations (an "Unconverted Debenture"), shall have the option, exercisable in
the Holder's sole and absolute discretion, to elect any one of the following
remedies:


                                       4
<PAGE>

            (x) if permitted by the Cap Regulations, require the Company to
      issue shares of Common Stock in accordance with such Holder's Notice of
      Conversion relating to the Unconverted Debenture at a conversion purchase
      price equal to the average of the closing price per share of Common Stock
      for any five (5) consecutive trading days (subject to the equitable
      adjustments for certain events occurring during such period as provided in
      this Debenture) during the sixty (60) trading days immediately preceding
      the date of the Notice of Conversion; or

            (y) require the Company to redeem each Unconverted Debenture for an
      amount (the "Cap Redemption Amount"), payable in cash, equal to:

                         V                      x           M
                  -----------------
                        CP

      where:

            "V" means the outstanding principal plus accrued interest through
      the Cap Redemption Date (as defined below) of an Unconverted Debenture;

            "CP" means the Conversion Rate in effect on the date of redemption
      (the "Cap Redemption Date") specified in the notice from the Holder
      electing this remedy; and

            "M" means the highest closing price during the period beginning on
      the Cap Redemption Date and ending on the date of payment of the Cap
      Redemption Amount.

The holder of an Unconverted Debenture may elect one of the above remedies with
respect to a portion of such Unconverted Debenture and the other remedy with
respect to other portions of the Unconverted Debenture.

      7. Subject to the terms of the Securities Purchase Agreement, dated
February17, 2000 (the "Securities Purchase Agreement"), between the Company and
the Holder (or the Holder's predecessor in interest), no provision of this
Debenture shall alter or impair the obligation of the Company, which is absolute
and unconditional, to pay the principal of, and interest on, this Debenture at
the time, place, and rate, and in the coin or currency, herein prescribed. This
Debenture and all other Debentures now or hereafter issued of similar terms are
direct obligations of the Company.

      8. No recourse shall be had for the payment of the principal of, or the
interest on, this Debenture, or for any claim based hereon, or otherwise in
respect hereof, against any incorporator, shareholder, officer or director, as
such, past, present or future, of the Company or any successor


                                       5
<PAGE>

corporation, whether by virtue of any constitution, statute or rule of law, or
by the enforcement of any assessment or penalty or otherwise, all such liability
being, by the acceptance hereof and as part of the consideration for the issue
hereof, expressly waived and released.

      9. If the Company merges or consolidates with another corporation or sells
or transfers all or substantially all of its assets to another person and the
holders of the Common Stock are entitled to receive stock, securities or
property in respect of or in exchange for Common Stock, then as a condition of
such merger, consolidation, sale or transfer, the Company and any such
successor, purchaser or transferee agree that the Debenture may thereafter be
converted on the terms and subject to the conditions set forth above into the
kind and amount of stock, securities or property receivable upon such merger,
consolidation, sale or transfer by a holder of the number of shares of Common
Stock into which this Debenture might have been converted immediately before
such merger, consolidation, sale or transfer, subject to adjustments which shall
be as nearly equivalent as may be practicable. In the event of any proposed
merger, consolidation or sale or transfer of all or substantially all of the
assets of the Company (a "Sale"), the Holder hereof shall have the right to
convert this Debenture by delivering a Notice of Conversion to the Company
within fifteen (15) days of receipt of notice of such Sale from the Company. In
the event the Holder hereof shall elect not to convert, the Company may (but
shall not be required to) prepay all outstanding principal and accrued interest
on this Debenture by paying the Redemption Amount contemplated by Section 5(A)
hereof, less all amounts required by law to be deducted, upon which tender of
payment following such notice, the right of conversion shall terminate.

      10. If, for any reason, prior to the Conversion Date or the Redemption
Payment Date, the Company spins off or otherwise divests itself of a part of its
business or operations or disposes all or of a part of its assets in a
transaction (the "Spin Off") in which the Company does not receive compensation
(other than nominal non-material compensation) for such business, operations or
assets, but causes securities of another entity (the "Spin Off Securities") to
be issued to security holders of the Company, then the Company shall cause (i)
to be reserved Spin Off Securities equal to the number thereof which would have
been issued to the Holder had all of the Holder's Debentures outstanding on the
record date (the "Record Date") for determining the amount and number of Spin
Off Securities to be issued to security holders of the Company (the "Outstanding
Debentures") been converted as of the close of business on the trading day
immediately before the Record Date (the "Reserved Spin Off Shares"), and (ii) to
be issued to the Holder on the conversion of all or any of the Outstanding
Debentures, such amount of the Reserved Spin Off Shares equal to (x) the
Reserved Spin Off Shares multiplied by (y) a fraction, of which (I) the
numerator is the principal amount of the Outstanding Debentures then being
converted, and (II) the denominator is the principal amount of the Outstanding
Debentures.

      11. If, at any time while any portion of this Debenture remains
outstanding, the Company effectuates a stock split or reverse stock split of its
Common Stock or issues a dividend on its Common Stock consisting of shares of
Common Stock, the Conversion Rate shall be equitably adjusted to reflect such
action. By way of illustration, and not in limitation, of the foregoing (i) if
the Company effectuates a 2:1 split of its Common Stock, thereafter, with
respect to any conversion


                                       6
<PAGE>

for which the Company issues the shares after the record date of such split, the
Conversion Rate shall be deemed to be one-half of what it had been calculated to
be immediately prior to such split; (ii) if the Company effectuates a 1:10
reverse split of its Common Stock, thereafter, with respect to any conversion
for which the Company issues the shares after the record date of such reverse
split, the Conversion Rate shall be deemed to be ten times what it had been
calculated to be immediately prior to such split; and (iii) if the Company
declares a stock dividend of one share of Common Stock for every 10 shares
outstanding, thereafter, with respect to any conversion for which the Company
issues the shares after the record date of such dividend, the Conversion Rate
shall be deemed to be the amount of such Conversion Rate calculated immediately
prior to such record date multiplied by a fraction, of which the numerator is
the number of shares (10) for which a dividend share will be issued and the
denominator is such number of shares plus the dividend share(s) issuable or
issued thereon (11).

      12. All payments contemplated hereby to be made "in cash" shall be made in
immediately available good funds in such coin or currency of the United States
of America as at the time of payment is legal tender for payment of public and
private debts. All payments of cash and each delivery of shares of Common Stock
issuable to the Holder as contemplated hereby shall be made to the Holder at the
address last appearing on the Debenture Register of the Company as designated in
writing by the Holder from time to time; except that the Holder can designate,
by notice to the Company, a different delivery address for any one or more
specific payments or deliveries.

      13. The Holder of the Debenture, by acceptance hereof, agrees that this
Debenture is being acquired for investment and that such Holder will not offer,
sell or otherwise dispose of this Debenture or the Shares of Common Stock
issuable upon conversion thereof except under circumstances which will not
result in a violation of the Act or any applicable state Blue Sky or foreign
laws or similar laws relating to the sale of securities.

      14. This Debenture shall be governed by and construed in accordance with
the laws of the State of Delaware. Each of the parties consents to the
jurisdiction of the federal courts whose districts encompass any part of the
City of Wilmington or the state courts of the State of Delaware sitting in the
City of Wilmington in connection with any dispute arising under this Agreement
and hereby waives, to the maximum extent permitted by law, any objection,
including any objection based on forum non coveniens, to the bringing of any
such proceeding in such jurisdictions. To the extent determined by such court,
the Company shall reimburse the Holder for any reasonable legal fees and
disbursements incurred by the Holder in enforcement of or protection of any of
its rights under any of this Debenture.

      15. The following shall constitute an "Event of Default":

            a.    The Company shall default in the payment of principal or
                  interest on this Debenture and same shall continue for a
                  period of five (5) days; or


                                       7
<PAGE>

            b.    Any of the representations or warranties made by the Company
                  herein, in the Securities Purchase Agreement, the Registration
                  Rights Agreement or in any certificate or financial or other
                  written statements heretofore or hereafter furnished by the
                  Company in connection with the execution and delivery of this
                  Debenture or the Securities Purchase Agreement shall be false
                  or misleading in any material respect at the time made; or

            c.    The Company fails to issue shares of Common Stock to the
                  Holder or to cause its Transfer Agent to issue shares of
                  Common Stock upon exercise by the Holder of the conversion
                  rights of the Holder in accordance with the terms of this
                  Debenture, fails to transfer or to cause its Transfer Agent to
                  transfer any certificate for shares of Common Stock issued to
                  the Holder upon conversion of this Debenture and when required
                  by this Debenture or the Registration Rights Agreement, and
                  such transfer is otherwise lawful, or fails to remove any
                  restrictive legend or to cause its Transfer Agent to transfer
                  on any certificate or any shares of Common Stock issued to the
                  Holder upon conversion of this Debenture as and when required
                  by this Debenture, the Agreement or the Registration Rights
                  Agreement and such legend removal is otherwise lawful, and any
                  such failure shall continue uncured for five (5) business
                  days.

            d.    The Company shall fail to perform or observe, in any material
                  respect, any other covenant, term, provision, condition,
                  agreement or obligation of any Debenture in this series and
                  such failure shall continue uncured for a period of thirty
                  (30) days after written notice from the Holder of such
                  failure; or

            e.    The Company shall fail to perform or observe, in any material
                  respect, any covenant, term, provision, condition, agreement
                  or obligation of the Company under the Securities Purchase
                  Agreement or the Registration Rights Agreement and such
                  failure shall continue uncured for a period of thirty (30)
                  days after written notice from the Holder of such failure
                  (other than a failure to cause the Registration Statement to
                  become effective no later than the Required Effective Date, as
                  defined and provided in the Registration Rights Agreement, as
                  to which no such cure period shall apply); or

            f.    The Company shall (1) admit in writing its inability to pay
                  its debts generally as they mature; (2) make an assignment for
                  the benefit of creditors or commence proceedings for its
                  dissolution; or (3) apply for or consent to the appointment of
                  a trustee, liquidator or receiver for its or for a substantial
                  part of its property or business; or


                                       8
<PAGE>

            g.    A trustee, liquidator or receiver shall be appointed for the
                  Company or for a substantial part of its property or business
                  without its consent and shall not be discharged within sixty
                  (60) days after such appointment; or

            h.    Any governmental agency or any court of competent jurisdiction
                  at the instance of any governmental agency shall assume
                  custody or control of the whole or any substantial portion of
                  the properties or assets of the Company and shall not be
                  dismissed within sixty (60) days thereafter; or

            i.    Any money judgment, writ or warrant of attachment, or similar
                  process in excess of Two Hundred Thousand ($200,000) Dollars
                  in the aggregate shall be entered or filed against the Company
                  or any of its properties or other assets and shall remain
                  unpaid, unvacated, unbonded or unstayed for a period of sixty
                  (60) days or in any event later than five (5) days prior to
                  the date of any proposed sale thereunder; or

            j.    Bankruptcy, reorganization, insolvency or liquidation
                  proceedings or other proceedings for relief under any
                  bankruptcy law or any law for the relief of debtors shall be
                  instituted by or against the Company and, if instituted
                  against the Company, shall not be dismissed within sixty (60)
                  days after such institution or the Company shall by any action
                  or answer approve of, consent to, or acquiesce in any such
                  proceedings or admit the material allegations of, or default
                  in answering a petition filed in any such proceeding; or

            k.    The Company shall have its Common Stock suspended or delisted
                  from an exchange or over-the-counter market from trading for
                  in excess of twenty (20) trading days.

Then, or at any time thereafter, and in each and every such case, unless such
Event of Default shall have been waived in writing by the Holder (which waiver
shall not be deemed to be a waiver of any subsequent default) at the option of
the Holder and in the Holder's sole discretion, the Holder may consider this
Debenture immediately due and payable, without presentment, demand, protest or
notice of any kinds, all of which are hereby expressly waived, anything herein
or in any note or other instruments contained to the contrary notwithstanding,
and the Holder may immediately enforce any and all of the Holder's rights and
remedies provided herein or any other rights or remedies afforded by law.

      16. Nothing contained in this Debenture shall be construed as conferring
upon the Holder the right to vote or to receive dividends or to consent or
receive notice as a shareholder in respect of any meeting of shareholders or any
rights whatsoever as a shareholder of the Company, unless and to the extent
converted in accordance with the terms hereof.


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<PAGE>

      17. In the event for any reason, any payment by or act of the Company or
the Holder shall result in payment of interest which would exceed the limit
authorized by or be in violation of the law of the jurisdiction applicable to
this Debenture, the ipso facto the obligation of the Company to pay interest or
perform such act or requirement shall be reduced to the limit authorized under
such law, so that in no event shall the Company be obligated to pay any such
interest, perform any such act or be bound by any requirement which would result
in the payment of interest in excess of the limit so authorized. In the event
any payment by or act of the Company shall result in the extraction of a rate of
interest in excess of a sum which is lawfully collectible as interest, then such
amount (to the extent of such excess not returned to the Company) shall, without
further agreement or notice between or by the Company or the Holder, be deemed
applied to the payment of principal, if any, hereunder immediately upon receipt
of such excess funds by the Holder, with the same force and effect as though the
Company had specifically designated such sums to be so applied to principal and
the Holder had agreed to accept such sums as an interest-free prepayment of this
Debenture. If any part of such excess remains after the principal has been paid
in full, whether by the provisions of the preceding sentences of this Section 17
or otherwise, such excess shall be deemed to be an interest-free loan from the
Company to the Holder, which loan shall be payable immediately upon demand by
the Company. The provisions of this Section 17 shall control every other
provision of this Debenture.

      IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed by an officer thereunto duly authorized.

Dated: February 17, 2000

                                    AMBIENT CORPORATION


                                    By:_______________________________________

                                    __________________________________________
                                    (Print Name)
                                    __________________________________________
                                    (Title)


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<PAGE>

                                    EXHIBIT A


                              NOTICE OF CONVERSION

   (To be Executed by the Registered Holder in order to Convert the Debenture)


      The undersigned hereby irrevocably elects to convert $ ________________ of
the principal amount of the above Debenture No. ___ into Shares of Common Stock
of AMBIENT CORPORATION (the "Company") according to the conditions hereof, as of
the date written below.


Conversion Date*
________________________________________________________________________________

Applicable Conversion Rate
________________________________________________________________________________


Signature
________________________________________________________________________________
                                     [Name]

Address:
________________________________________________________________________________

________________________________________________________________________________


* This original Debenture must be received by the Company or its transfer agent
by the fifth business date following the Conversion Date.