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                                                                    EXHIBIT 4.3

                         SECOND SUPPLEMENTAL INDENTURE

         Supplemental Indenture (this "Supplemental Indenture"), dated as of
July 11, 2000, by and among Fenix Holdings, Inc., a Florida corporation ("Fenix
Holdings"), Hattech, Inc., a Florida corporation ("Hattech"), Irwin Telecom
Services, Inc., a Florida corporation ("Irwin"), Fenix Telecommunications
Services, Inc., a Florida corporation ("Fenix Telecomm"), Network Comprehensive
Telecom, LP, a Texas limited partnership ("Network Telecomm"), Network Cabling
Holdings, Inc., a Florida corporation ("Network Holdings"), Midwest Splicing &
Activation, Inc., a Minnesota corporation ("Midwest" and together with Fenix
Holdings, Hattech, Irwin, Fenix Telecomm, Network Telecomm and Network
Holdings, the "Guaranteeing Subsidiaries"), NATG Holdings, Inc., a Delaware
limited liability company ("NATG"), Orius Capital Corp., a Delaware corporation
(together with NATG, the "Issuers"), Orius Corp., a Florida corporation
("Parent"), the subsidiaries of Parent named in the Indenture (as hereinafter
defined) as guarantors (together with Parent, the "Original Guarantors") and
United States Trust Company of New York, as trustee (the "Trustee") under the
Indenture. Capitalized terms used herein without definition shall have the
meanings assigned to them in the Indenture.

         WITNESSETH

         WHEREAS, the Issuers and the Original Guarantors have previously
executed and delivered to the Trustee an indenture (as supplemented from time
to time, the "Indenture"), dated as of February 9, 2000, providing for the
issuance of an aggregate principal amount of up to $300,000,000 of 12 3/4%
Senior Subordinated Notes due 2010;

         WHEREAS, the Indenture provides that the Guaranteeing Subsidiaries
shall execute and deliver to the Trustee a supplemental indenture pursuant to
which the Guaranteeing Subsidiaries shall unconditionally guarantee all of the
Issuers' obligations under the Securities and the Indenture on the terms and
conditions set forth in the Indenture; and

         WHEREAS, pursuant to Section 9.1 of the Indenture, the Trustee is
authorized to execute and deliver this Supplemental Indenture.

         NOW THEREFORE, in consideration of the foregoing and for other good
and valuable consideration, the receipt of which is hereby acknowledged, the
parties hereto mutually covenant and agree for the equal and ratable benefit of
the Holders of the Securities as follows:

         1. Agreement to Guarantee. The Guaranteeing Subsidiaries hereby agree
as follows:

         (a)      Along with all Guarantors named in the Indenture, to jointly
                  and severally, unconditionally and irrevocably guarantee, on
                  a senior subordinated basis (each such guarantee to be
                  referred to herein as a "Note Guarantee") to each Holder of a
                  Security authenticated and delivered by the Trustee and to
                  the Trustee and its successors and assigns, irrespective of
                  the validity and enforceability of the Indenture, this
                  Supplemental Indenture, the Securities or the obligations of
                  the Issuers or any other Guarantors to the Holders or the
                  Trustee hereunder or thereunder, that: (i) the

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                  principal of, premium, if any, and interest on the Securities
                  shall be duly and punctually paid in full when due, whether
                  at maturity, upon redemption at the option of Holders
                  pursuant to the provisions of the Securities relating
                  thereto, by acceleration or otherwise, and interest on the
                  overdue principal and (to the extent permitted by law)
                  interest, if any, on the Securities and all other obligations
                  of the Issuers or the Guarantors to the Holders or the
                  Trustee hereunder or thereunder (including amounts due the
                  Trustee under Section 7.7 of the Indenture) and all other
                  obligations shall be promptly paid in full or performed, all
                  in accordance with the terms hereof and thereof; and (ii) in
                  case of any extension of time of payment or renewal of any
                  Securities or any of such other obligations, the same shall
                  be promptly paid in full when due or performed in accordance
                  with the terms of the extension or renewal, whether at
                  maturity, by acceleration or otherwise. Failing payment when
                  due of any amount so guaranteed, or failing performance of
                  any other obligation of the Issuers to the Holders under the
                  Indenture or under the Securities, for whatever reason, each
                  Guaranteeing Subsidiary shall be obligated to pay, or to
                  perform or cause the performance of, the same immediately. An
                  Event of Default under the Indenture or the Securities shall
                  constitute an event of default under this Note Guarantee, and
                  shall entitle the Holders of Securities to accelerate the
                  obligations of the Guaranteeing Subsidiaries hereunder in the
                  same manner and to the same extent as the obligations of the
                  Issuers.

         (b)      The Guaranteeing Subsidiaries' obligations hereunder shall be
                  unconditional, irrespective of the validity, regularity or
                  enforceability of the Securities or this Supplemental
                  Indenture, the absence of any action to enforce the same, any
                  waiver or consent by any Holder of the Securities with
                  respect to any provisions hereof or thereof, any release of
                  any other Guarantor, the recovery of any judgment against an
                  Issuer, any action to enforce the same, whether or not a
                  Guarantee is affixed to any particular Security, or any other
                  circumstance which might otherwise constitute a legal or
                  equitable discharge or defense of a Guarantor. Each of the
                  Guaranteeing Subsidiaries hereby waive the benefit of
                  diligence, presentment, demand of payment, filing of claims
                  with a court in the event of insolvency or bankruptcy of an
                  Issuer, any right to require a proceeding first against an
                  Issuer, protest, notice and all demands whatsoever and
                  covenants that its Note Guarantee shall not be discharged
                  except by complete performance of the obligations contained
                  in the Securities, the Indenture and this Note Guarantee.
                  This Note Guarantee is a guarantee of payment and not of
                  collection. If any Holder or the Trustee is required by any
                  court or otherwise to return to the Issuers or to any
                  Guarantor, or any custodian, trustee, liquidator or other
                  similar official acting in relation to an Issuer or such
                  Guarantor, any amount paid by an Issuer or such Guarantor to
                  the Trustee or such Holder, this Note Guarantee, to the
                  extent theretofore discharged, shall be reinstated in full
                  force and effect. Each Guarantor further agrees that, as
                  between it, on the one hand, and the Holders of Securities
                  and the Trustee, on the other hand, (i) subject to the
                  provisions hereof, the maturity of the obligations guaranteed
                  hereby may be accelerated as provided in

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                  Article Six of the Indenture for the purposes of this Note
                  Guarantee, notwithstanding any stay, injunction or other
                  prohibition preventing such acceleration in respect of the
                  obligations guaranteed hereby, and (ii) in the event of any
                  acceleration of such obligations as provided in Article Six
                  of the Indenture, such obligations (whether or not due and
                  payable) shall forthwith become due and payable by the
                  Guaranteeing Subsidiaries for the purpose of this Note
                  Guarantee.

         (c)      Each Guaranteeing Subsidiary that makes a payment or
                  distribution under a Note Guarantee shall be entitled to a
                  contribution from each other Guarantor on a pro rata basis,
                  based on the net assets of each Guarantor, determined in
                  accordance with GAAP.

         (d)      The Obligations of each Guaranteeing Subsidiary under its
                  Note Guarantee are limited to the maximum amount which, after
                  giving effect to all other contingent and of the Senior
                  Secured Credit Agreement and any other Guarantor Senior Debt,
                  and after giving effect to any collections from or payments
                  made by or on behalf of any other Guarantor in respect of the
                  obligations of such other Guarantor under its Guarantee or
                  pursuant to its contribution obligations under the Indenture,
                  will result in the obligations of such Guaranteeing
                  Subsidiary under the Note Guarantee not constituting a
                  fraudulent conveyance or fraudulent transfer under federal or
                  state law.

         4. Incorporation of Terms of Indenture. The obligations of the
Guaranteeing Subsidiaries under the Note Guarantees shall be governed in all
respects by the terms of the Indenture and shall constitute a Guarantee
thereunder. Each of the parties hereto shall be bound by the terms of the
Indenture as they relate to the Note Guarantees.

         5. No Recourse Against Others. No stockholder, officer, director,
employee or incorporator, past, present or future, or any Guaranteeing
Subsidiary, as such, shall have any personal liability under this Note
Guarantee by reason of his, her or its status as such stockholder, officer,
director, employee or incorporator.

         6. NEW YORK LAW TO GOVERN. THE INTERNAL LAW OF THE STATE OF NEW YORK
SHALL GOVERN AND BE USED TO CONSTRUE THIS SUPPLEMENTAL INDENTURE BUT WITHOUT
GIVING EFFECT TO APPLICABLE PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT
THE APPLICATION OF THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

         7. Counterparts. The parties may sign any number of copies of this
Supplemental Indenture. Each signed copy shall be an original, but all of them
together represent the same agreement.

         8. Effect of Headings. The Section headings herein are for convenience
only and shall not affect the construction hereof.

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         9. Disclaimer by Trustee. The Trustee makes no representation as to
the validity of this Supplemental Indenture or the proper authorization or due
execution of this Supplemental Indenture by the Issuers, the Original
Guarantors or the Guaranteeing Subsidiaries.

                                   * * * * *

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IN WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture
to be duly executed and attested, all as of the date first above written.

Dated: June __, 2000             ORIUS CORP.*
                                 ORIUS CAPITAL CORP.*
                                 NORTH AMERICAN TEL-COM GROUP, INC.*
                                 CATV SUBSCRIBER SERVICES, INC.
                                 CABLEMASTERS CORP.
                                 CHANNEL COMMUNICATIONS, INC.
                                 EXCEL CABLE CONSTRUCTION, INC.
                                 MICH-COM CABLE SERVICES INCORPORATED
                                 STATE WIDE CATV, INC.
                                 U.S. CABLE, INC.
                                 DAS-CO OF IDAHO, INC.
                                 NETWORK CABLING SERVICES, INC.
                                 NETWORK CABLING HOLDINGS, INC.*
                                 SCHATZ UNDERGROUND CABLE, INC.
                                 COPENHAGEN UTILITIES & CONSTRUCTION, INC.
                                 TEXEL CORPORATION*
                                 LISN COMPANY
                                 ARION SUB, INC.
                                 LISN, INC.
                                 IRWIN TELECOM HOLDINGS, INC.
                                 IRWIN TELECOM SERVICES, INC.
                                 FENIX HOLDINGS, INC.*
                                 FENIX TELECOMMUNICATIONS SERVICES, INC.*
                                 MIDWEST SPLICING & ACTIVATION, INC.
                                 HATTECH, INC.

                                 /s/ WILLIAM J. MERCURIO
                                 ---------------------------------------------
                                 William J. Mercurio, Executive Vice President
                                 President of those companies designated
                                          with an asterix


                                 FENIX TELECOM SERVICES LIMITED PARTNERSHIP

                                 By: Fenix Telecommunications Services, Inc.
                                 Its: General Partner

                                 /s/ WILLIAM J. MERCURIO
                                 ---------------------------------------------
                                 William J. Mercurio
                                 President


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                [Signature Page to Supplemental Indenture cont.]

                                 IRWIN TELECOM SERVICES, L.P.
                                 By: Irwin Telecom Services, Inc.
                                 Its: General Partner

                                 /s/ WILLIAM J. MERCURIO
                                 ---------------------------------------------
                                 William J. Mercurio
                                 Executive Vice President

                                 NETWORK COMPREHENSIVE TELECOM, L.P.
                                 By: Network Cabling Services, Inc.
                                 Its: General Partner

                                 /s/ WILLIAM J. MERCURIO
                                 ---------------------------------------------
                                 William J. Mercurio
                                 Executive Vice President

                                 NATG HOLDINGS, LLC
                                 By: Orius Corp.
                                 Its: Sole Member

                                 /s/ WILLIAM J. MERCURIO
                                 ---------------------------------------------
                                 William J. Mercurio
                                 President


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                [Signature Page to Supplemental Indenture cont.]

                                 UNITED STATES TRUST COMPANY OF NEW YORK, AS
                                 TRUSTEE

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



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