Document:

<PAGE>   1

                                                                  EXHIBIT 4.21.1

          AMENDMENT NO. 1 TO SECURITIES EXCHANGE AGREEMENT AND RELATED
           REGISTRATION RIGHTS AGREEMENT OF ABLE TELCOM HOLDING CORP.

This Amendment No. 1 ("Amendment No. 1") dated as of July 7, 2000 to the
Securities Exchange Agreement dated as of February 4, 2000 ("Exchange
Agreement"), by and among Halifax Fund, L.P., The Gleneagles Fund Company,
Palladin Overseas Fund Limited, Colonial Penn Life Insurance Company, Palladin
Securities, L.L.C. and Palladin Partners I, L.P. (collectively, "Holders") and
Able Telcom Holding Corp. (the "Company"), and an amendment to a related
Registration Rights Agreement entered into by the holders and the Company
pursuant to the Exchange Agreement as specifically described herein.

                                    RECITALS

         WHEREAS, in June 1998 the Company issued, pursuant to a Purchase
Agreement (the "Series B Purchase Agreement") to the Holders, 404 shares of
Series B Preferred Stock, and in connection therewith, the Holders and the
Company entered into a Registration Rights Agreement substantially in the form
of Exhibit A hereto (the "Series B Registration Rights Agreement"), the Articles
of Amendment substantially in the form of Exhibit B hereto (the "Series B
Articles of Amendment") and other documents related to the issuance of Series B
Preferred Stock and included as exhibits to the Company's public filings with
the Securities and Exchange Commission (the "Series B Agreements" and
collectively with the Series B Registration Rights Agreement and the Series B
Articles of Amendment, the "Series B Documents"); and

         WHEREAS, in February 2000 the Holders and the Company entered into the
Exchange Agreement, a copy of which is attached as Exhibit C and incorporated by
reference herein, whereby, in exchange for the surrender to the Company by the
Holders of 154 Preferred Shares (constituting all the Company's Series B
Preferred Shares then still held by the Holders), the Company issued 301,787
shares of Company Common Stock, $0.001 par value per share (the "Common Stock"),
plus $5,816,394 in cash, and the registration rights and warrants described in
the next succeeding paragraphs; and

         WHEREAS, Section 1.2 of the Exchange Agreement provides that an
additional amount of cash will be paid to the Holders by the Company 100 Trading
Days after the date of the date of the Exchange Agreement;

         WHEREAS, the Company and the Holders, as of February 4, 2000, entered
into a Registration Rights Agreement ("Exchange Registration Rights Agreement")
substantially in the form of Exhibit D attached hereto and incorporated by
reference herein, to provide for the registration of the shares of Common Stock
issued to the Holders pursuant to the Exchange Agreement; and

         WHEREAS, the Company issued to the Holders warrants for 66,246 shares
of Common

                                     - 1 -
<PAGE>   2

Stock, referred to as the "First Exchange Warrants", a form of the First
Exchange Warrant being substantially in the form as Exhibit E hereto and which
form shall be incorporated by reference herein; and

         WHEREAS, the Company issued to the Holders warrants for 100,000 shares
of Common Stock, referred to as the "Second Exchange Warrants", a form of the
Second Exchange Warrant being substantially in the form as Exhibit F hereto
which form shall be incorporated by reference herein; and

         WHEREAS, the Company and the Holder are entering into this Amendment
No. 1 in connection with the Company's settlement of its obligation to Sirit
Technologies, Inc. ("Sirit"), as described in the Agreement between the Sirit
Parties and the Able Parties (as each of those terms are defined in the Sirit
Agreement) dated as of July 7, 2000 (the "Sirit Agreement"); and

         WHEREAS, the Holders and the Company wish in this Amendment No. 1 to
amend the Exchange Agreement and the Exchange Registration Rights Agreement, but
not the First Exchange Warrant or the Second Exchange Warrant or the other
Series B Documents (together, the "Transaction Documents"); and

         WHEREAS, the Company will, as promptly as possible, call and hold a
shareholders meeting to consider and approve (1) an amendment to the Company's
Articles of Incorporation to increase the number of shares of authorized Common
Stock to 100,000,000 shares of Common Stock; (2) one or more proposals to issue
the shares of Common Stock pursuant to this Amendment No. 1 and pursuant to
certain other agreements between the Holder and the Company; and (3) a proposal
to issue shares of Common Stock pursuant to the Sirit Agreement (matters (1),
(2) and (3) together, the "Shareholder Proposals").

         NOW, THEREFORE, intending to be legally bound hereby, the Parties agree
that all capitalized terms not defined herein shall have the meanings ascribed
to them in the Exchange Agreement and as follows:

1.       Recitals. The above recitals are true, correct and incorporated herein
by reference.

2.       Amendment to Section 1.2 of the Exchange Agreement.

         Section 1.2 of the Exchange Agreement shall be revised and restated in
its entirety to read as follows:

                  "On or before December 1, 2000, the Company shall issue to the
         Holders, pro rata in accordance with the number of shares purchased by
         the Holders at the Closing, 1,057,031 shares of Common Stock; provided
         that the Company's shareholders have, prior to December 1, 2000,
         approved the Shareholder Proposals. In the event that the shareholders
         have not, prior to December 1, 2000, approved the Shareholder
         Proposals, upon demand at the option of the Holders in lieu of issuing
         such shares, the Company shall pay to the Holders, pro rata, $4,228,124
         in cash, by wire transfer or (b) the Company shall upon

                                     - 2 -
<PAGE>   3

         demand by the Holders at any time after the Shareholder Proposals have
         been approved, issue such shares of Common Stock."

3.       Amendment to Exchange Registration Rights Agreement to Revise
Definition of Registration Deadline.

         The term "Registration Deadline" in Section 1 of the Exchange
Registration Agreement shall be amended and restated in its entirety to read as
follows:

                  "Registration Deadline" shall mean the date the Company, using
                  its Best Efforts, is able to secure the effectiveness of the
                  Registration Statement (defined herein); provided, however,
                  that in no event shall the Registration Deadline be later than
                  November 30, 2000."

4.       Agreement with Respect to Bankruptcy.

         The Holders agree not to place Able in involuntary bankruptcy from the
date of this Agreement until either (a) if the Sirit Shares are issued prior to
December 1, 2000, 91 days following the issuance of the Sirit Shares; or (b) if
the Sirit Shares are not issued by December 1, 2000, for 91 days following the
date on which the Consent Judgment has been paid or satisfied in full, but in no
event later than May 31, 2001.

5.       Proxy.

         Each of the Holders shall execute a form of proxy attached to this
Amendment No. 1 as Exhibit "F" whereby the Holders agrees to vote any shares of
Common Stock held by the Holders in support of the Shareholder Proposals.

6.       Condition to Effectiveness of Amendment No. 1.

         This Amendment No. 1 shall not be effective until all of the conditions
contained in Section XI (other than Condition XI.B. which is covered by this
Amendment No. 7) of the Sirit Agreement have been satisfied in full (unless
waived by the Holders).

         The Company shall inform the Holders in writing upon the satisfaction
of such conditions. The Holders may waive satisfaction of such conditions at any
time.

7.       Miscellaneous.

         a.       Entire Understanding. This Amendment No. 1, together with the
Transaction Documents, contains the entire understanding of the parties with
respect to the matters covered hereby. Except as set forth in this Amendment No.
1, the terms of the Transaction Documents shall remain in full force and effect.

                                     - 3 -
<PAGE>   4

         b.       Further Actions. The Company and the Holders acknowledge that
this Amendment No. 1 is being entered into in connection with the Company's
settlement of its obligation to Sirit arising out of certain litigation with the
Sirit. The Company and the Holders agree that they shall take such further
actions as may be required to effect the intent and purpose of this Amendment
No. 1, including the filing of amended Articles of Amendment and the execution
of any further amendments to any of the Transaction documents, as may be
reasonably requested by the Company or any Investor, to carry out the purpose
and intention of this Agreement.

         c.       Governing Law. This Amendment No. 1 shall be governed by and
construed and enforced in accordance with the laws of the State of New York
applicable to agreements executed and to be performed entirely within such state
and, where applicable, federal law.

         d.       Counterpart Signatures. This Amendment No. 1 may be executed
in two or more counterparts, all of which shall be considered one and the same
amendment, it being understood that all parties need not sign the same
counterpart.

         e.       Construction. The language in this Amendment No. 1 will be
deemed to be the language chosen by the parties to express their mutual intent,
and no rules of strict construction shall be applied against any party.

         f.       Conflict with other Documents. To the extent that the
provisions of any of the Transaction Documents conflict with this Amendment No.
1, the terms of this Amendment No. 1 shall govern provided that, the parties
acknowledge and agree that if any references to section or paragraph number are
not accurately reflected in this Amendment No. 1, then this Amendment No. 1
shall be amended to reflect such changes without any further actions on the part
of any of the parties.

                          [SIGNATURES ON THE NEXT PAGE]

                                     - 4 -
<PAGE>   5

IN WITNESS WHEREOF, the Parties hereto have caused this Amendment No. 1 to be
executed as of the day and year first above written.

                        HOLDERS:

                        HALIFAX FUND, L.P.
                        THE GLENEAGLES FUND COMPANY
                        PALLADIN OVERSEAS FUND LIMITED
                        COLONIAL PENN LIFE INSURANCE
                        COMPANY

                        By:
                               -------------------------------------------------
                               The Palladin Group, L.P., as Attorney-in-Fact and
                               Investment Advisor
                        Name:  Robert L. Chender
                        Title: Managing Director

                        PALLADIN SECURITIES L.L.C.

                        By:
                               -------------------------------------------------
:                       Name:  Robert L. Chender
                        Title: Principal

                        PALLADIN PARTNERS I, L.P.

                        By:
                               -------------------------------------------------
                               The Palladin Group, L.P., as Attorney-in-Fact and
                               Investment Advisor
                        Name:  Robert L. Chender
                        Title: Managing Director

                        ABLE TELCOM HOLDING CORP.

                        By:
                               -------------------------------------------------
                        Name:
                               -------------------------------------------------
                        Title
                               -------------------------------------------------

                                     - 5 -
<PAGE>   6

                                   EXHIBIT "F"

                            ABLE TELCOM HOLDING CORP.
                                      PROXY

I appoint Michael Brenner and Edward Z. Pollock, or either one, the
undersigned's proxy to vote all of its shares of common stock of Able Telcom
Holding Corp. that are entitled to vote at any meeting of Able Telcom Holding
Corp. shareholders called to approve the Shareholder Proposals (as defined in
Amendment No. 1 to the Securities Exchange Agreement and related Registration
Rights Agreement of the Company and the undersigned dated as of July 7, 2000),
including the proposal to issue to Sirit Technologies shares of Common Stock
pursuant to the Settlement Agreement, dated July 7, 2000 (the "Sirit
Agreement"), between the "Sirit Parties" and the "Able Parties"; as each of
those terms is defined in the Sirit Agreement, a copy of which Sirit Agreement
is attached as Exhibit "A," in favor of the Shareholder Proposals. This proxy
shall expire and be of no further force and effect after December 1, 2000.

----------------, --------

(Complete above date and sign your name as it appears below. If more than one
name appears, each person should sign).

----------------------------------------

                                             By:
                                                 -------------------------------
                                             Name:
                                                   -----------------------------
                                             Its:
                                                  ------------------------------
                                             Number of shares of common stock
----------------------------------------

                                     - 6 -<PAGE>   1

                                                                  EXHIBIT 4.22.1

        AMENDMENT NO. 1 TO ABLE TELCOM HOLDING CORP. SERIES C CONVERTIBLE
           PREFERRED STOCK PURCHASE AGREEMENT AND RELATED AGREEMENTS

This Amendment No. 1 ("Amendment No. 1") dated July 7, 2000 amends (i) the
Convertible Preferred Stock Purchase Agreement ("Purchase Agreement") dated as
of February 4, 2000 between Able Telcom Holding Corp., a Florida corporation
(the "Company"), and each person or entity listed as an Investor on Schedule I
to this Amendment No. 1 (each, individually, an "Investor" and, collectively,
the "Investors") and (ii) certain other related agreements referenced in this
Amendment No. 1.

                              W I T N E S S E T H:

         WHEREAS, the Company and the Investors entered into the Purchase
Agreement pursuant to which the Investors purchased 5,000 shares of Series C
Convertible Preferred Stock (the "Series C Preferred Stock/Preferred Shares")
from the Company, which Series C Preferred Stock has the rights and remedies set
forth in the Articles of Amendment setting forth the terms of the Series C
Preferred Stock ("Articles of Amendment") in the form of Exhibit A attached
hereto and incorporated herein by reference; and

         WHEREAS, the Company and the Investors, as of February 4, 2000, entered
into a Registration Rights Agreement ("Registration Rights Agreement")
substantially in the form of Exhibit B attached hereto and incorporated herein
by reference; and

         WHEREAS, the Company issued to the Investors warrants ("Series C
Warrants") to purchase up to 200,000 shares of common stock, $0.001 par value
per share, of the Company ("Common Stock"), a form of warrant being
substantially in the form as Exhibit C hereto and incorporated herein by
reference (the Purchase Agreement, the Articles of Amendment, the Registration
Right Agreement and the Series C Warrants, collectively, the "Transaction
Documents"); and

         WHEREAS, the Company and the Investors are entering into this Amendment
No. 1 in connection with the Company's settlement of its obligation to Sirit
Technologies, Inc. ("Sirit"), as described in the Agreement between the Sirit
Parties and the Able Parties (as each of those terms are defined in the Sirit
Agreement) dated as of July 7, 2000 (the "Sirit Agreement").

         WHEREAS, the Company will, as promptly as possible, call and hold a
shareholders meeting to consider and approve (1) an amendment to the Company's
Articles of Incorporation to increase the number of shares of authorized Common
Stock to 100,000,000 shares of Common Stock; (2) one or more proposals to issue
the shares of Common Stock pursuant to this Amendment No. 1 and pursuant to
certain other agreements between the Investors and the Company; and (3) a
proposal to issue shares of Common Stock pursuant to the Sirit Agreement
(matters (1), (2) and (3) together, the "Shareholder Proposals").

                                       1
<PAGE>   2

         NOW, THEREFORE, in consideration of the foregoing premises and the
covenants herein contained and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties hereto
agree that all capitalized terms used herein and not defined herein shall have
the meanings ascribed to them in the respective Transaction Document and as
follows:

1.       Recitals. The above recitals are true, correct and incorporated herein
         by reference.

2.       Amendments Affecting Conversion Price Contained in Articles of
         Amendment.

         Section 3(b)(iii) of the Articles of Amendment shall be amended and
restated in its entirety to read as follows:

         "'Conversion Price' shall mean, as of any Conversion Date (as defined
in Section 3(e)) or other date of determination, a price equal to $4.00."

3.       Permitted Issuance of Shares to Sirit and the Investors.

         Section 3(c)(i) of the Articles of Amendment shall be amended to add
the following clause to the end of the parenthetical in the first sentence of
Section 3(A):

         "or (z) pursuant to Section II(B)(1) of the Agreement between Sirit
Technologies, Inc., the Company and certain other parties as specified therein,
dated July 7, 2000 or (xx) to any of the Investors or any "Holder" or "Holders",
as such terms are defined in (A) Amendment No. 1 to the Securities Exchange
Agreement of Able Telcom Holding Corp. dated July 7, 2000 between the Company
and Halifax Fund, L.P., The Gleneagles Fund Company, Palladin Partners I, L.P
(the "Amendment No. 1 to the Palladin Exchange Agreement"), or (B) Amendment No.
1 to the Securities Exchange Agreement of Able Telcom Holding Corp. dated July
7, 2000 between the Company and RGC International Investors, LDC (the "Amendment
No. 1 to the RoseGlen Exchange Agreement")."

4.       Limitation on Number of Shares of Common Stock that may be Issued to
         Holders Prior to November 30, 2000.

         Subject to the provisions of Section 3(c) (ii), (iii), (iv) and (iv) of
the Articles of Amendment and notwithstanding any adjustment to the Conversion
Price that may have occurred pursuant to Section 3(c)(i) of the Articles of
Amendment, the Investors agree that they shall not, prior to November 30, 2000,
convert (on a pro rata basis according to the Investors' holdings of Series C
Preferred Stock immediately after the Closing under the Purchase Agreement)
shares of Series C Preferred Stock to acquire more than 3,750,000 shares of
Common Stock.

5.       Dividends.

         Section (2) of the Articles of Amendment shall be amended to add the
following sentence to the end of such Section:

                                       2
<PAGE>   3

         "Notwithstanding the foregoing, all dividends that will have accrued
through November 30, 2000 shall be paid in cash on or before December 1, 2000
and shall not accrete to the Liquidation Value; provided that to the extent any
such dividends are not paid by the Company in cash for any reason on or before
December 1, 2000, such dividends not so paid shall accrete to the Liquidation
Value.

6.       Conversion Rights.

         Notwithstanding anything else in this Agreement or any of the
Transaction Documents to the contrary, the Investors hereby agree that they
shall not convert any of their Preferred Shares until the earlier to occur of
(i) shareholder approval having been obtained to (A) issue shares of Common
Stock to the Investors pursuant to the Articles of Amendment; and (B) increase
its authorized capital stock to 100,000,000 shares of Common Stock; and (ii)
December 1, 2000.

7.       Amendment to Redemption Right in Articles of Amendment.

         Section 3(f)(i) of the Articles of Amendment shall be amended and
restated in its entirety to read as follows:

                  (i) First Company Redemption Rights. Subject to the
                  restrictions and conditions contained in paragraphs (a) and
                  (b) of this Section 3 and the exercise by any holder of its
                  right to redeem Preferred Shares under Section 4, commencing
                  on the later of either 60 days after the Registration
                  Statement first becomes effective or December 31, 2000, the
                  Company may, at its option, from time to time, require all
                  holders to redeem their Preferred Shares, in whole or in part
                  as specified by the Company (such redemption, a "FIRST COMPANY
                  REDEMPTION"), at the Company Redemption Price (as defined
                  below) pursuant to a Company Redemption Notice following the
                  procedures set forth in Section 3(f)(iv); provided, however,
                  that no First Company Redemption shall be permitted unless the
                  Registration Statement has been effective under the Securities
                  Act of 1933, as amended (the "ACT"), for at least 60
                  consecutive days preceding the date of such Company Redemption
                  Notice; and any such Company Redemption Notice shall be void
                  with respect to any Preferred Shares that shall have been
                  converted prior to the effective date of such Company
                  Redemption Notice. A First Company Redemption under this
                  Section 3(f)(i) shall be effective upon the close of business
                  on the 30th calendar day after the date that the Company
                  Redemption Notice is received by each holder. Nothing in this
                  Section 3(f) shall be construed to preclude the holders from
                  being permitted, notwithstanding a Company Redemption Notice,
                  to convert any or all Preferred Shares to the extent provided
                  by Section 3(a) prior to the effective date of a Company
                  Redemption Notice. The "COMPANY REDEMPTION PRICE" shall be the
                  sum of (A) the Liquidation Value at

                                       3
<PAGE>   4

                  the effective date of the First Company Redemption, plus (B)
                  10% of such Liquidation Value for each whole or partial
                  six-month period between the Closing Date and the effective
                  date of the First Company Redemption.

8.       Amendment to Definition of Registration Deadline in Registration Rights
         Agreement.

         The definition of "Registration Deadline" in Section 1 of the
Registration Rights Agreement is hereby amended and restated in its entirety to
read as follows:

         "Registration Deadline" shall mean the date the Company, using its Best
         Efforts, is able to secure the effectiveness of the Registration
         Statement (defined herein); provided, however, that in no event shall
         the Registration Deadline be later than November 30, 2000.

9.       Amendment to Right of First Refusal Contained in Purchase Agreement.

         The parenthetical contained in the first sentence of Section 3.18 shall
be amended to add at the end thereof the following clause:

         "or in connection with (A) Amendment No. 1 to the Palladin Exchange
Agreement, (B) Amendment No. 1 to the Rose Glen Exchange Agreement, and (c) the
issuance to Sirit Technologies, Inc. shares of Common Stock pursuant to Section
II(B)(1) of the Agreement dated July 7, 2000 between Sirit and the Company and
certain other parties as specified therein".

10.      Issuances of Equity.

         Section 3(d) of the Articles of Amendment is modified to provide that
the Company may issue equity securities, instruments or rights convertible or
into or exchangeable or exercisable for, equity securities in connection with or
relating to (i) Section II.B.1 of the Sirit Agreement; and (ii) any shares of
Common Stock issued to any of the Investors or any "Holder" or "Holders", as
such terms are defined in (A) the Amendment No. 1 to the Palladin Exchange
Agreement, or (B) the Amendment No. 1 to the RoseGlen Exchange Agreement.

10A.     Rescission of Section 5.1 of the Purchase Agreement

         Section 5.1 (Investor Rights to Purchase Additional Shares) of the
         Purchase Agreement is hereby terminated and deleted in its entirety.

10B.     Additional Warrants

         The Company agrees to issue additional warrants to the Investors, such
         warrants to be substantially in the form of the Series C Warrants, to
         have the benefit of the Registration Rights Agreement and to be in two
         series, each with a term of two years, one series for 375,000 shares of
         Common Stock exercisable at $6.00 per share and the second series for
         375,000 of Common Stock exercisable at $8.00 per share.

                                       4
<PAGE>   5

11.      Proxy.

         Each of the Investors shall execute a form of proxy attached to this
Amendment No. 1 as Exhibit "F" whereby each Investor agrees to vote any shares
of Common Stock held by such Investor in support of the Shareholder Proposals.

12.      Delay in Exercise of Monetary and Other Remedies.

         Other than as specifically contemplated by this Amendment No.1 (or any
other agreement entered into between the Company and the Investors and any
affiliates of the Investors of even date), each of the Investors agrees that
they will not provide a Notice of Redemption upon Triggering Event until after
December 1, 2000 under Section 4(b) of the Articles of Amendment.

13.      Condition to Effectiveness of Amendment No. 1.

         This Amendment No. 1 shall not be effective until all of the conditions
contained in Section XI (other than Section XIB, which is covered by this
Amendment No. 1) of the Sirit Agreement have been satisfied in full (unless
waived by the Investors).

         The Company shall inform the Investors in writing when such conditions
shall have been satisfied. The Investors may waive satisfaction of such
conditions at any time.

14.      Agreement with Respect to Bankruptcy.

         The Investors agree not to place Able in involuntary bankruptcy from
the date of this Agreement until either (a) if the Sirit Shares are issued prior
to December 1, 2000, 91 days following the issuance of the Sirit Shares; or (b)
if the Sirit Shares are not issued by December 1, 2000, for 91 days following
the date on which the Consent Judgment has been paid or satisfied in full, but
in no event later than May 31, 2001.

15.      Call Feature of the Company.

         Notwithstanding any provision of the Purchase Agreement or Articles of
Amendment to the contrary, at any time prior to August 31, 2000 the Company
shall have the right, at the Company's option, upon prior written notice, to
require all of the Holders to tender their Preferred Shares for redemption at a
redemption price of $3600 per Preferred Share payable in cash; provided however,
the Holders may elect in their sole discretion to convert their Preferred Shares
into Common Stock at the Conversion Price of $4.00 per share; provided that such
conversion shall not be prohibited by or be in derogation of any securities laws
or rules including without limitation any NASDAQ marketplace rules specifically
NASDAQ marketplace rule 4460(l).

                                       5
<PAGE>   6

16.      Miscellaneous.

         a.       Entire Understanding. This Amendment No. 1, together with the
Transaction Documents, contains the entire understanding of the parties with
respect to the matters covered hereby. Except as expressly set forth in this
Amendment No. 1, the terms of the Transaction Documents remain in full force and
effect.

         b.       Further Actions. The Company and the Investors acknowledge
that this Amendment No. 1 is being entered into in connection with the Company's
settlement of its obligation to Sirit arising out of certain litigation with
Sirit. The Company and the Investors agree that they shall take such further
actions, including the filing of amended Articles of Amendment and the execution
of any further amendments to any of the Transaction documents, as may be
reasonably requested by the Company or any Investor, to carry out the purpose
and intention of this Amendment.

         c.       Governing Law. This Amendment No. 1 shall be governed by and
construed and enforced in accordance with the laws of the State of New York
applicable to agreements executed and to be performed entirely within such state
and, where applicable, federal law.

         d.       Counterpart Execution. This Amendment No. 1 may be executed in
two or more counterparts, all of which shall be considered one and the same
amendment, it being understood that all parties need not sign the same
counterpart.

         e.       Construction. The language in this Amendment No. 1 will be
deemed to be the language chosen by the parties to express their mutual intent,
and no rules of strict construction shall be applied against any party.

         f.       Conflict with Other Documents. To the extent that the
provisions of any of the Transaction Documents conflict with this Amendment No.
1, the terms of this Amendment No. 1 shall govern; provided that the parties
acknowledge and agree that if any references to section or paragraph numbers are
not accurately reflected in this Amendment No. 1., then this Amendment No. 1
shall be amended to reflect such changes without any further actions on the part
of any of the parties.

                          [SIGNATURES ON THE NEXT PAGE]

                                       6
<PAGE>   7

         IN WITNESS WHEREOF, the Parties hereto have caused this Amendment No. 1
to be duly executed as of the date first above written.

                                      ABLE TELCOM HOLDING CORP.

                                      By:
                                          --------------------------------------
                                      Name: Billy V. Ray, Jr.,
                                      Title: Chairman of the Board

                                      INVESTORS:
HALIFAX FUND, L.P.

                                      By: The Palladin Group, L.P.,
                                          as Investment Manager
By:
    ---------------------------            Name: Robert L. Chender
                                           Title: Managing Director

                                      THE GLENEAGLES FUND COMPANY

                                      By: The Palladin Group, L.P., as
                                          Investment Manager

                                      By:
                                          --------------------------------------
                                           Name: Robert L. Chender
                                           Title: Managing Director

                                      PALLADIN OVERSEAS FUND LIMITED

                                      By: The Palladin Group, L.P., as
                                          Investment Manager

                                      By:
                                          --------------------------------------
                                           Name: Robert L. Chender
                                           Title: Managing Director

                                       7
<PAGE>   8

                                      PALLADIN PARTNERS I, L.P.

                                      By: Palladin Asset Management, LLC
                                          as Investment Manager

                                      By:
                                          --------------------------------------
                                          Name:
                                          Title:

                                      LANCER SECURITIES (CAYMAN) LIMITED

                                      By: The Palladin Group, L.P., as
                                          Investment Manager

                                      By:
                                          --------------------------------------
                                          Name: Robert L. Chender
                                          Title: Managing Director

                                      PGEP III, LLC

                                      By: The Palladin Group, L.P., as
                                          Investment Manager

                                      By:
                                          --------------------------------------
                                          Name: Robert L. Chender
                                          Title: Managing Director

                                      QUATTRO FUND LIMITED

                                      By: Quattro Investors LP

                                      By:
                                          --------------------------------------
                                          Name: Andrew Kaplan
                                          Title: Principal

                                       8
<PAGE>   9

                                   SCHEDULE I

Halifax Fund, L.P.

The Gleneagles Fund Company

Palladin Overseas Fund Limited

Palladin Partners I, L.P.

Lancer Securities (Cayman) Limited

PGEP III, LLC

Quarrto Fund Limited

                                       9
<PAGE>   10

                                   EXHIBIT "F"

                            ABLE TELCOM HOLDING CORP.
                                      PROXY

I appoint Michael Brenner and Edward Z. Pollock, or either one, the
undersigned's proxy to vote all of its shares of common stock of Able Telcom
Holding Corp. that are entitled to vote at any meeting of Able Telcom Holding
Corp. shareholders called to approve the Shareholder Proposals (as defined in
Amendment No. 1 to Able Telcom Holding Corp. Series C Convertible Preferred
Stock Purchase Agreement and Related Agreements dated as of July 7, 2000,
including the proposal to issue to Sirit Technologies shares of Common Stock
pursuant to the Settlement Agreement dated July 7, 2000 (the "Sirit Agreement")
between the "Sirit Parties" and the "Able Parties"; as each of those terms is
defined in the Sirit Agreement, a copy of which Sirit Agreement is attached as
Exhibit "A," in favor of the Shareholder Proposals. This proxy shall expire and
be of no further force and effect after December 1, 2000.

----------------, --------

(Complete above date and sign your name as it appears below. If more than one
name appears, each person should sign).

                                           -------------------------------------

                                           By:
                                               ---------------------------------
                                           Name:
                                                 -------------------------------
                                           Its:
                                                --------------------------------

                                           Number of shares of common stock

                                           -------------------------------------

                                       10

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