<PAGE>   1
                                                                     EXHIBIT 4.3

         THIS WARRANT AND THE SHARES OF COMMON STOCK ISSUABLE UPON EXERCISE
         HEREOF HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
         AMENDED (THE "ACT"), OR ANY STATE SECURITIES OR BLUE SKY LAWS AND MAY
         NOT BE OFFERED, SOLD, TRANSFERRED, HYPOTHECATED OR OTHERWISE ASSIGNED
         EXCEPT (1) PURSUANT TO A REGISTRATION STATEMENT WITH RESPECT TO SUCH
         SECURITIES WHICH IS EFFECTIVE UNDER THE ACT OR (2) PURSUANT TO AN
         AVAILABLE EXEMPTION FROM REGISTRATION UNDER THE ACT RELATING TO THE
         DISPOSITION OF SECURITIES AND (3) IN ACCORDANCE WITH APPLICABLE STATE
         SECURITIES AND BLUE SKY LAWS.

                                    WARRANT
         WARRANT TO PURCHASE FIFTY ONE THOUSAND SIX HUNDRED SIXTY FOUR
                        (51,664) SHARES OF COMMON STOCK
                                       OF
                       SONUS COMMUNICATION HOLDINGS, INC.
                       DATE OF ISSUANCE: JANUARY 27, 2000
                                 NO.__________

         THIS CERTIFIES that, for value received, L. Flomenhaft & Co., Inc., or
its assigns (in either case, the "Holder") is entitled to purchase, subject to
the provisions of this Warrant, from SONUS COMMUNICATION HOLDINGS, INC., a
Delaware corporation (the "Company"), at the price per share set forth in
Section 8 hereof, the number of shares of the Company's common stock, $.0001
par value per share (the "Common Stock"), set forth in Section 7 hereof.  This
Warrant is referred to herein as the "Warrant" and the shares of Common Stock
issuable pursuant to the terms hereof are sometimes referred to herein as
"Warrant Shares". Capitalized terms used but not defined herein shall have the
respective meanings accorded such terms in the Subscription Agreement.

         Section 7.       Exercise of Warrant.  To exercise this Warrant in
whole or in part, the Holder shall deliver to the Company at its principal
office, (a) a written notice, in substantially the form of the exercise notice
attached hereto (the "Exercise Notice"), of the Holder's election to exercise
this Warrant, which notice shall specify the number of shares of Common Stock
to be purchased, (b) a check in the amount of the aggregate exercise price for
the Warrant Shares being purchased, and (c) this Warrant.  The Company shall as
promptly as practicable, and in any event within twenty (20) days after
delivery to the Company of (i) the Exercise Notice, (ii) the check mentioned
above, and (iii) this Warrant, execute and deliver or cause to be executed and
delivered, in accordance with such notice, a certificate or certificates
representing the aggregate number of shares of Common Stock specified in such
notice, provided the Warrants specified in such notice have vested on or prior
to the date such notice is delivered.  If the Holder elects to purchase, at any
time, less than the number of shares of Common Stock then purchasable under the
terms of this Warrant, the Company shall issue to the Holder a new Warrant
exercisable into the number of remaining shares of Common Stock purchasable
under this Warrant.  Each certificate representing Warrant Shares shall bear
the legend or legends required by applicable securities laws as well as such
other legend(s) the Company requires to be included on certificates for its
Common Stock.  The Company shall pay all expenses, taxes and other charges
payable in connection with the preparation, issuance and delivery of such stock
certificates except that, in case such stock certificates shall be registered
in a name or names other than the name of the Holder, funds sufficient to pay
all stock transfer taxes that are payable upon the issuance of such stock
certificate or certificates shall be paid by the Holder at the time of
delivering the Exercise Notice.  All shares of Common Stock issued upon the
exercise of this Warrant shall be validly issued, fully paid, and
nonassessable.  This Warrant may be exercised on





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multiple occasions in amounts not less than 15% of the original amount issued
before the expiration of its term as described in this Section 1.  This Warrant
will expire on January 27, 2005 (the "Expiration Date").

     Section 8.        Reservation of Shares.  The Company hereby covenants
that at all times during the term of this Warrant there shall be reserved for
issuance such number of shares of its Common Stock as shall be required to be
issued upon exercise of this Warrant.

     Section 9.        Fractional Shares.  This Warrant may be exercised only
for a whole number of shares of Common Stock, and no fractional shares or scrip
representing fractional shares shall be issuable upon the exercise of this
Warrant.

  Transfer of Warrant and Warrant Shares.  The Holder may sell, pledge,
hypothecate, or otherwise transfer this Warrant, in whole or in part, only in
accordance with and subject to the terms and conditions set forth in the
Subscription Agreement and then only if such sale, pledge, hypothecation, or
transfer is made in compliance with the Act or pursuant to an available
exemption from registration under the Act relating to the disposition of
securities, and is made in accordance with applicable State securities laws.

  Loss of Warrant.  Upon receipt by the Company of evidence satisfactory to it
of the loss, theft, or destruction of this Warrant, and of indemnification
satisfactory to it, or upon surrender and cancellation of this Warrant, if
mutilated, the Company will execute and deliver a new Warrant of like tenor.

  Rights of the Holder.  No provision of this Warrant shall be construed as
conferring upon the Holder the right to vote, consent, receive dividends or
receive notice other than as expressly provided herein.  Prior to exercise, no
provision hereof, in the absence of affirmative action by the Holder to
exercise this Warrant, and no enumeration herein of the rights or privileges of
the Holder, shall give rise to any liability of the Holder for the purchase
price of any Warrant Shares or as a stockholder of the Company, whether such
liability is asserted by the Company or by creditors of the Company.

  Number of Warrant Shares.  This Warrant shall be exercisable for up to Fifty
One Thousand Six Hundred and Sixty Four (51,664) shares of the Company's Common
Stock, as adjusted in accordance with this Agreement.

  Exercise Price; Redemption; Adjustment of Warrants. Determination of Exercise
Price. The per share purchase price (the "Exercise Price") for each of the
Warrant Shares purchasable under this Warrant shall be equal to One Dollar and
Thirty Five Cents ($1.35).

         (b)     Redemption of Warrants. The Warrants are redeemable by the
Company at $0.05 per Warrant (the "Redemption Price"), upon 20 days notice, at
the discretion of the Company, when the following three conditions have been
met: (i) a registration statement has been filed under the Securities Act
covering the resale of the Shares, Warrants and the Warrant Shares, and such
registration statement is effective, (ii) a public market has developed for the
Common Stock, and (iii) the bid price of the Common Stock has closed at $4.50
or higher for ten consecutive trading days.  Redemption of the Warrants shall
be automatically effective and the Warrants shall be deemed cancelled upon the
Company's delivery of the Redemption Price to the Holder in accordance with
this Agreement.  Upon receipt of the Redemption Price, Holder agrees to return
any evidence of the Warrants to the Company.

         (c)     Adjustments for Stock Dividends, Distributions and
Subdivisions. If the Company at any time or from time to time after the
original issue date shall declare or pay any dividend or distribution on the
Common Stock payable in Common Stock, or effect a subdivision of the
outstanding shares of Common Stock into a greater number of shares of Common
Stock (by reclassification or otherwise than by payment of a dividend in Common
Stock), then the number of shares of Common Stock into which this Warrant is
exercisable shall be increased to an amount which is equal to the product of
(i) the number of shares of Common Stock for which this Warrant is exercisable
immediately prior to the stock dividend, distribution or subdivision, as the
case may be, and (ii) a fraction, the numerator of which is equal to the number
of shares of Common Stock issued and outstanding after giving effect to such
stock dividend, distribution or subdivision, and the denominator of which is
the number of shares of Common Stock issued and outstanding prior to such stock
dividend, distribution or subdivision. If the outstanding shares





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of Common Stock shall be divided or increased because of a stock dividend or
distribution, by stock split or otherwise, into a greater number of shares of
Common Stock, the Exercise Price in effect immediately prior to such dividend,
distribution or division shall, concurrently with the effectiveness of such
division, dividend or distribution, be proportionately decreased.





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         (d)     Adjustments for Combinations or Consolidation of Common Stock.
If the outstanding shares of Common Stock shall be combined or consolidated, by
reclassification, reverse stock split or otherwise, into a lesser number of
shares of Common Stock, then the number of shares of Common Stock into which
this Warrant is exercisable shall be decreased to an amount which is equal to
the product of (i) the number of shares of Common Stock for which this Warrant
is exercisable immediately prior to combination or consolidation, as the case
may be, and (ii) a fraction, the numerator of which is equal to the number of
shares of Common Stock issued and outstanding after giving effect to such
combination or consolidation, and the denominator of which is the number of
shares of Common Stock issued and outstanding prior to such combination or
consolidation. If the outstanding shares of Common Stock shall be combined or
consolidated, by reclassification, reverse stock split or otherwise, into a
lesser number of shares of Common Stock, the Exercise Price in effect
immediately prior to such combination or consolidation shall, concurrently with
the effectiveness of such combination or consolidation, be proportionately
increased.

         (e)     Adjustment for Mergers or Reorganization, etc.  In case of any
consolidation or merger of the Company with or into another corporation or the
conveyance of all or substantially all of the assets of the Company to another
corporation, this Warrant shall be exercisable into the number of shares of
stock or other securities or property to which a holder of the number of shares
of Common Stock of the Company deliverable upon exercise of this Warrant would
have been entitled upon such consolidation, merger or conveyance; and, in any
such case, appropriate adjustment (as determined by the Board of  Directors of
the Company) shall be made in the application of the provisions herein set
forth with respect to the rights and interest thereafter of the holder of this
Warrant, to the end that the provisions set forth herein shall thereafter be
applicable, as nearly as reasonable may be, in relation to any shares of stock
or other property thereafter deliverable upon the exercise of this Warrant.

         (f)     No Impairment.  The Company will not, through any
reorganization, transfer of assets, consolidation, merger, dissolution, issue
or sale of securities or any other voluntary action, avoid or seek to avoid the
observance or performance of any of the terms to be observed or performed
hereunder by the Company, but will at all times in good faith assist in the
carrying out of all the provisions of this Section 8 and in the taking of all
such action as may be necessary or appropriate in order to protect the exercise
rights of the holder of this Warrant against impairment.

         (g)     Issue Taxes.  The Company shall pay any and all issue and
other taxes that may be payable in respect of any issue or delivery of shares
of Common Stock on exercise of this Warrant, in whole or in part; provided,
however, that the Company shall not be obligated to pay any transfer taxes
resulting from any transfer requested by any holder in connection with any such
exercise.

         (h)     Reservation of Stock Issuable Upon Conversion.  The Company
shall at all times reserve and keep available out of its authorized but
unissued shares of Common Stock, solely for the purpose of effecting the
exercise of this Warrant, such number of its shares of Common Stock as shall
from time to time be sufficient to effect the exercise of this Warrant; and if
at any time the number of authorized but unissued shares of Common Stock shall
not be sufficient to effect the exercise of this Warrant, the Company will take
all appropriate corporate action as may, in the opinion of its counsel, be
necessary to increase its authorized but unissued shares of Common Stock to
such number of shares as shall be sufficient for such purpose.

         (i)     Fractional Shares.  No fractional share shall be issued upon
the exercise, in whole or in part, of this Warrant.  If any exercise in whole
or in part of this Warrant would result in the issuance of a fraction of a
share of Common Stock, the Company shall, in lieu of issuing any fractional
share, pay the holder otherwise entitled to such fraction a sum in cash equal
to the fair market value of such fraction on the date of exercise (as
determined in good faith by the Board of Directors of the Company).

         Section 9.       Certain Distributions.  In case the Company shall, at
any time, prior to the Expiration Date set forth in Section 1 hereof, declare
any distribution of its assets to holders of its Common Stock as a partial
liquidation, distribution or by way of return of capital, other than as a
dividend payable out of earnings or any surplus legally available for
dividends, then the Holder shall be





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entitled, upon the proper exercise of this Warrant in whole or in part prior to
the effecting of such declaration, to receive, in addition to the shares of
Common Stock issuable on such exercise, the amount of such assets (or at the
option of the Company a sum equal to the value thereof at the time of such
distribution to holders of Common Stock as such value is determined by the
Board of Directors of the Company in good faith), which would have been payable
to the Holder had it been a holder of record of such shares of Common Stock on
the record date for the determination of those holders of Common Stock entitled
to such distribution.

         Section 10.      Dissolution or Liquidation.  In case the Company
shall, at any time prior to the Expiration Date set forth in Section 1 hereof,
dissolve, liquidate or wind up its affairs, the Holder shall be entitled, upon
the proper exercise of this Warrant in whole or in part and prior to any
distribution associated with such dissolution, liquidation, or winding up, to
receive on such exercise, in lieu of the shares of Common Stock to which the
Holder would have been entitled, the same kind and amount of assets as would
have been distributed or paid to the Holder upon any such dissolution,
liquidation or winding up, with respect to such shares of Common Stock had the
Holder been a holder of record of such share of Common Stock on the record date
for the determination of those holders of Common Stock entitled to receive any
such dissolution, liquidation, or winding up distribution.

         Section 11.      Reclassification or Reorganization.  In case of any
reclassification, capital reorganization or other change of outstanding shares
of Common Stock of the Company (other than a change in par value, or from par
value to no par value, or from no par value to par value, or as a result of an
issuance of Common Stock by way of dividend or other distribution or of a
subdivision or combination), the Company shall cause effective provision to be
made so that the Holder shall have the right thereafter by exercising this
Warrant, to purchase the kind and amount of shares of stock and other
securities and property receivable upon such reclassification, capital
reorganization or other change, by a holder of the number of shares of Common
Stock which might have been purchased upon exercise of this Warrant immediately
prior to such reclassification or change.  Any such provision shall include
provision for adjustments which shall be as nearly equivalent as may be
practicable to the adjustments provided for in this Warrant.  The foregoing
provisions of this Section 11 shall similarly apply to successive
reclassifications, capital reorganizations and changes of shares of Common
Stock.  In the event that in any such capital reorganization, reclassification,
or other change, additional shares of Common Stock shall be issued in exchange,
conversion, substitution or payment, in whole or in part, for or of a security
of the Company other than Common Stock, any amount of the consideration
received upon the issue thereof being determined by the Board of Directors of
the Company shall be final and binding on the Holder.

         Section 12.  Miscellaneous.

                 (a)  Successors and Assigns. The terms and conditions of this
Agreement shall inure to the benefit of, and be binding upon, the respective
successors and assigns of the parties, except to the extent otherwise provided
herein.  Nothing in this Agreement, express or implied, is intended to confer
upon any party, other than the parties hereto or their respective successors
and assigns, any rights, remedies, obligations or liabilities under or by
reason of this Agreement, except as expressly provided in this Agreement.

                 (b)  Governing Law.  This Agreement shall be governed by and
construed in accordance with the laws of the State of Delaware, without regard
to the principles of conflict of laws thereof.

                 (c)  Counterparts; Delivery by Facsimile.  This Agreement may
be executed in one or more counterparts, each of which shall be deemed an
original, but all of which together shall constitute one and the same
instrument.  Delivery of this Agreement may be effected by facsimile.

                 (d)  Titles and Subtitles.  The titles and subtitles used in
this Agreement are used for convenience only and are not to be considered in
construing or interpreting this Agreement.

                 (e)  Notices.  Unless otherwise provided, any notice required
or permitted hereunder shall be given by personal service upon the party to be
notified, by nationwide overnight delivery service or upon deposit with the
United States Post Office, by certified mail, return receipt requested and:





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                          i.  if to the Company, addressed to SONUS
COMMUNICATION HOLDINGS, INC., 1600 Wilson Blvd., Suite 1008, Arlington,
Virginia 22209, Attention: W. Todd Coffin, with a copy to Cecil E. Martin, III,
Esquire, McGuire, Woods Battle & Booth LLP, Seven Saint Paul Street, Suite
1000, Baltimore, Maryland 21202- 1626, or at such other address as the Company
may designate by notice to each of the Investors in accordance with the
provisions of this Section; and

                          ii.  if to the Warrant holder, at the address
indicated on the signature pages hereof, or at such other addresses as such
Holder may designate by notice to the Company in accordance with the provisions
of this Section.

                 (f)  Amendments and Waivers.  Any term of this Agreement may
be amended and the observance of any term of this Agreement may be waived
(either generally or in a particular instance and either prospectively or
retroactively), only with the written consent of the Company and a majority in
interest of the Holders.

                 (g)  Entire Agreement.  This Agreement and the Subscription
Agreement (including the exhibits and schedules hereto) constitute the entire
agreement among the parties hereto with respect to the subject matter hereof
and thereof and supersede all prior agreements, understandings, negotiations
and discussions, whether oral or written, of the parties hereto.





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         IN WITNESS WHEREOF, the undersigned hereby sets is hand and seal this
__ day of _____, 2000.

                              SONUS COMMUNICATION HOLDINGS, INC.

                              By:  /s/ W. Todd Coffin
                                   -----------------------------------
                              Name:   W. Todd Coffin
                              Title:  Chief Executive Officer


                              Investor Name: L. Flomenhaft & Co., Inc.
                              Investor Address:
                                               -------------------------





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                                EXERCISE NOTICE


Dated: _____________________

         The undersigned hereby irrevocably elects to exercise his, her or its
right to purchase _________ shares of the common stock, $.0001 par value per
share (the "Common Stock"), of SONUS COMMUNICATION HOLDINGS, INC., a Delaware
corporation (the "Company"), such right being pursuant to a Warrant dated
_________, 2000, and as issued to the undersigned by the Company, and remits
herewith the sum of $______ in payment for same in accordance with the Exercise
Price specified in Section 8 of said Warrant.





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                                ASSIGNMENT FORM


Dated: _____________________

         For value received ____________________ hereby sells, assigns and
         transfers unto
         Name: ____________________________________________
                          (Please typewrite or print block letters)
         Address:   _______________________________________
                    _______________________________________

    and appoints:   _______________________________________
                    _______________________________________

Attorney to transfer the said Warrant on the books of SONUS COMMUNICATION
HOLDINGS, INC. with full power of substitution in the premises.

                                 Signature: ______________________________





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