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                                                                    Exhibit 4.5


                            SECOND SUPPLEMENTAL INDENTURE


     SECOND SUPPLEMENTAL INDENTURE, dated as of October 30, 1998 (this "Second
Supplemental Indenture"), among Wavetek Wandel & Goltermann, Inc. (the
"Company"), Digital Transport Systems, Inc. ("DTS") and The Bank of New York, as
trustee (the "Trustee").

                                W I T N E S S E T H:

     WHEREAS, the Company, Wandel & Goltermann Technologies, Inc., Wandel & 
Goltermann A.T.E. Systems, Inc., Wandel & Goltermann, Inc., W&G Equities, 
Inc. and the Trustee are parties to an Indenture, dated as of June 11, 1997 
and supplemented as of September 30, 1998 (the "Indenture"), providing for 
the issuance of $85,000,000 of the Company's 10 1/8% Senior Subordinated 
Notes due June 15, 2007 (the "Notes");

     WHEREAS, effective as of September 30, 1998, DTS became a Subsidiary (as
defined in the Indenture) of the Company;

     WHEREAS, pursuant to Section 4.16 and Section 10.02 of the Indenture, DTS
is required to become a Subsidiary Guarantor (as defined in the Indenture) under
the Indenture and execute and deliver a Subsidiary Guarantee (as defined in the
Indenture);

     NOW, THEREFORE, each party agrees as follows for the benefit of each other
and for the equal ratable benefit of the holders of the Notes:

     1.   SUBSIDIARY GUARANTEE.  DTS agrees to execute and deliver a Subsidiary
Guarantee and agrees to be bound by the terms of the Indenture as a Subsidiary
Guarantor.  The obligations of each Subsidiary Guarantor to the holders of the
Notes and to the Trustee pursuant to the Indenture are set forth in Article 10
of the Indenture, which terms are incorporated herein by reference.

     2.   CONFIRMATION OF INDENTURE.  The Indenture, as supplemented by this
Second Supplemental Indenture, is in all respects ratified and confirmed, and
the Indenture, this Second Supplemental Indenture and all indentures
supplemental thereto shall be read, taken and construed as one and the same
instrument.

     3.   CONCERNING THE TRUSTEE.  The Trustee assumes no duties,
responsibilities or liabilities by reason of this Second Supplemental Indenture
other than as set forth in the Indenture and, in carrying out its
responsibilities hereunder, shall have all of the rights, protections and
immunities which it possesses under the Indenture.

     4.   GOVERNING LAW.  This Second Supplemental Indenture and the Subsidiary
Guarantee shall be governed by and construed in accordance with the law of the
State of New York.

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     5.   COUNTERPARTS.  This Second Supplemental Indenture may be executed in
any number of counterparts each of which shall be an original, but such
counterparts shall together constitute but one and the same instrument.

     IN WITNESS WHEREOF, the parties hereto have caused this First Supplemental
Indenture to be duly executed, and the Subsidiary Guarantor has caused its
corporate seal to be hereunto affixed and attested, as of the day and year first
above written.


                                       DIGITAL TRANSPORT SYSTEMS, INC.

     [seal]
                                       By: /s/ VICKIE CAPPS
                                           -----------------------------------
                                           Name: Vickie Capps
                                           Title: Vice President, Treasurer and 
                                                  Secretary

Attest:


/s/ Gene Jones
----------------------------------
Name: Gene Jones
Title: President


                                       WAVETEK WANDEL & GOLTERMANN, INC.

     [seal]
                                       By: /s/ VICKIE CAPPS
                                           -----------------------------------
                                           Name: Vickie Capps
                                           Title: Senior Vice President - 
                                                  Finance

Attest:


/s/ Terence J. Gooding
---------------------------------
Name: Terence J. Gooding
Title: Co-Chairman


                                       THE BANK OF NEW YORK


                                       By: /s/ Thomas C. Knight
                                           -----------------------------------
                                           Name:  Thomas C. Knight
                                           Title: Assistant Vice President