<PAGE>
                                                                    EXHIBIT 10.3


                                SECOND AMENDMENT


            SECOND AMENDMENT (this "Amendment"), dated as of May 14, 1999, among
MJD COMMUNICATIONS, INC., a Delaware corporation (the "Borrower"), the lenders
from time to time party to the Credit Agreement referred to below (the
"Lenders"), NATIONSBANK OF TEXAS, N.A., as Syndication Agent (the "Syndication
Agent"), and BANKERS TRUST COMPANY, as Administrative Agent (the "Administrative
Agent" and together with the Syndication Agent, collectively, the "Agents").
Unless otherwise indicated, all capitalized terms used herein and not otherwise
defined shall have the respective meanings provided such terms in the Credit
Agreement referred to below.


                              W I T N E S S E T H :


            WHEREAS, the Borrower, the Lenders and the Agents are parties to a
Credit Agreement, dated as of March 30, 1998 (as amended, modified or
supplemented to the date hereof, the "Credit Agreement"); and

            WHEREAS, subject to and on the terms and conditions set forth
herein, the parties hereto wish to amend the Credit Agreement, as provided
below;

            NOW, THEREFORE, it is agreed:

            1.    Section 3.02(A) of the Credit Agreement is hereby amended by
deleting clause (c) of said Section in its entirety and inserting the following
new clause (c) in lieu thereof:

            "(c) On the fifth Business Day following the date of receipt thereof
      by the Borrower and/or any of its Subsidiaries of the Net Cash Proceeds
      from any Asset Sale, an amount equal to 100% of the Net Cash Proceeds from
      such Asset Sale shall be applied as a mandatory repayment of principal of
      the then outstanding Term Loans and if no Term Loans are then outstanding,
      to the RF Loans and the AF Loans, PRO RATA, among such Loans, PROVIDED
      that up to 100% of the Net Cash Proceeds from Asset Sales shall not be
      required to be used to so repay Loans to the extent (i) the Borrower
      elects, as hereinafter provided, to cause such Net Cash Proceeds to be
      used within 180 days of such Asset Sale to finance an Acquisition or
      Acquisitions or Permitted Acquisitions (a "Reinvestment Election") or (ii)
      in the case of Net Cash Proceeds from a Non-Core Asset Sale and so long as
      RF Loans in an aggregate principal amount equal to at least such amount of
      Net Cash Proceeds were incurred to finance an Acquisition or Acquisitions
      or Permitted Acquisitions within 90 days (or, in the case of the Net Cash
      Proceeds from the sale of certain Non-Core Assets of Taconic Technology
      Corp. and Taconic Telephone Corp., 120 days) prior to the date of receipt
      of such Net Cash Proceeds, the Borrower applies all (and not less than
      all) of such Net Cash Proceeds to repay outstanding principal of RF Loans

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      in accordance with Section 3.01 (a "Repayment Election"). The Borrower may
      exercise (x) its Repayment Election with respect to a Non-Core Asset Sale
      if (A) no Default or Event of Default exists and (B) the Borrower delivers
      a written notice signed by an Authorized Officer of the Borrower to the
      Administrative Agent no later than five Business Days following the
      respective Non-Core Asset Sale stating that it has incurred RF Loans in an
      aggregate principal amount equal to or greater than the Net Cash Proceeds
      received from such Non-Core Asset Sale to finance an Acquisition and/or
      Permitted Acquisition within the time period specified in clause (ii)
      above and specifying the relevant Acquisition(s) and/or Permitted
      Acquisition(s) consummated during such period and (y) its Reinvestment
      Election with respect to an Asset Sale if (A) no Default or Event of
      Default exists and (B) the Borrower delivers a Reinvestment Notice to the
      Administrative Agent no later than five Business Days following the date
      of the consummation of the respective Asset Sale, with such Reinvestment
      Election being effective with respect to the Net Cash Proceeds of such
      Asset Sale equal to the Anticipated Reinvestment Amount specified in such
      Reinvestment Notice."

            2.    Section 9 of the Credit Agreement is modified by inserting the
following new definitions in appropriate alphabetical order:

            "Non-Core Asset Sale" shall mean an Asset Sale constituting a sale
      of Non-Core Assets.

            "Repayment  Election"  shall have the meaning  provided in Section
      3.02(A)(c).

            3.    In order to induce the Lenders to enter into this Amendment,
the Borrower hereby (i) makes each of the representations, warranties and
agreements contained in Section 5 of the Credit Agreement and (ii) represents
and warrants that there exists no Default or Event of Default, in each case on
the Second Amendment Effective Date (as defined below), both before and after
giving effect to this Amendment.

            4.    This Amendment is limited as specified and shall not
constitute a modification, acceptance or waiver of any other provision of the
Credit Agreement or any other Credit Document.

            5.    This Amendment may be executed in any number of counterparts
and by the different parties hereto on separate counterparts, each of which
counterparts when executed and delivered shall be an original, but all of which
shall together constitute one and the same instrument. A complete set of
counterparts shall be lodged with the Borrower and the Administrative Agent.

            6.    THIS AMENDMENT AND THE RIGHTS AND OBLIGATIONS OF THE PARTIES
HEREUNDER SHALL BE CONSTRUED IN ACCORDANCE WITH AND GOVERNED BY THE LAW OF THE
STATE OF NEW YORK.

            7.    This Amendment shall become effective on the date (the "Second
Amendment Effective Date") when each of the Borrower and the Required Lenders
shall have


                                      -2-
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signed a counterpart hereof (whether the same or different counterparts) and
shall have delivered (including by way of facsimile transmission) the same to
White & Case LLP, 1155 Avenue of the Americas, New York, NY 10036 Attention:
John Giambalvo (facsimile number 212-354-8113).

            8.    From and after the Second Amendment Effective Date, all
references to the Credit Agreement in the Credit Agreement and the other Credit
Documents shall be deemed to be references to the Credit Agreement as modified
hereby.


                                      * * *



                                      -3-
<PAGE>


            IN WITNESS WHEREOF, each of the parties hereto has caused a
counterpart of this Amendment to be duly executed and delivered as of the date
first above written.



                                       MJD COMMUNICATIONS, INC.



                                       By: /s/ Timothy W. Henry
                                          --------------------------------------
                                          Name:  Timothy W. Henry
                                          Title: VP of Finance



                                       BANKERS TRUST COMPANY, Individually
                                          and as Administrative Agent



                                       By: /s/ Mary Kay Coyle
                                          --------------------------------------
                                          Name:
                                          Title:



                                       NATIONSBANK OF TEXAS, N.A.,
                                          Individually and as Syndication
                                          Agent



                                       By: /s/ Pamela S. Kurtzman
                                          --------------------------------------
                                          Name:  Pamela S. Kurtzman
                                          Title: Vice President



                                       COBANK, ACB



                                       By: /s/ Rick Freeman
                                          --------------------------------------
                                          Name:  Rick Freeman
                                          Title: Vice President


                                      -4-
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                                       FIRST UNION NATIONAL BANK



                                       By: /s/ Mark L. Cook
                                          --------------------------------------
                                          Name:  Mark L. Cook
                                          Title: Senior Vice President



                                       MORGAN STANLEY DEAN WITTER PRIME
                                          INCOME TRUST



                                       By: /s/ Shiela Finnerty
                                          --------------------------------------
                                          Name:  Shiela Finnerty
                                          Title: Vice President



                                       HELLER FINANCIAL, INC.



                                       By: /s/ K. Craig Gailehugh
                                          --------------------------------------
                                          Name:  K. Craig Gailehugh
                                          Title: Vice President



                                       THE TRAVELERS INSURANCE COMPANY



                                       By: /s/ Allen R. Cantrell
                                          --------------------------------------
                                          Name:  Allen R. Cantrell
                                          Title: Investment Officer



                                       UNION BANK OF CALIFORNIA, N.A.



                                       By: /s/ Ryan D. Flanagan
                                          --------------------------------------
                                          Name:  Ryan D. Flanagan
                                          Title: Assistant Vice President



                                      -5-
<PAGE>


                                       CENTURA BANK



                                       By: /s/ Gregory S. Greer
                                          --------------------------------------
                                          Name:  Gregory S. Greer
                                          Title: Corporate Banking Officer



                                       CIT GROUP/EQUIPMENT FINANCING INC.



                                       By: /s/ Ahmet Beyhan
                                          --------------------------------------
                                          Name:  Ahmet Beyhan
                                          Title: Sr. Credit Analyst



                                       FLEET NATIONAL BANK



                                       By: /s/ Tanya M. Crossley
                                          --------------------------------------
                                          Name:  Tanya M. Crossley
                                          Title: Vice President



                                       DELANO COMPANY
                                          By:  Pacific Investment Management
                                          Company as its Investment Advisor



                                       By: /s/ Mohan V. PhanSalkar
                                          --------------------------------------
                                          Name:  Mohan V. PhanSalkar
                                          Title: Senior Vice President



                                       MEESPIERSON CAPITAL CORP.



                                       By: /s/ Scott Webster
                                          --------------------------------------
                                          Name:  Scott Webster
                                          Title: Vice President



                                       By: /s/ Svein Engh
                                          --------------------------------------
                                          Name:  Svein Engh
                                          Title: Managing Director





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                                       SENIOR DEBT PORTFOLIO
                                          By BOSTON MANAGEMENT AND RESEARCH,
                                          as Investment Manager



                                       By:/s/ Payson F. Swaffield
                                          --------------------------------------
                                          Name:  Payson F. Swaffield
                                          Title: Vice President



                                       OXFORD STRATEGIC INCOME FUND
                                          By:  Eaton Vance Management as
                                          Investment Advisor


                                       By: /s/ Payson E. Swaffield
                                          --------------------------------------
                                          Name:  Payson E. Swaffield
                                          Title: Vice President