<PAGE>   1


Exhibit 10.1.3
                                        
                                                        EXECUTION COPY


                       AMENDMENT NO. 2 AND WAIVER NO. 2
                                      TO
                               CREDIT AGREEMENT


        THIS AMENDMENT NO. 2 AND WAIVER NO. 2 TO CREDIT AGREEMENT ("Agreement")
is being executed and delivered as of April 8, 1998 by and among Code-Alarm,
Inc., a Michigan corporation (the "Borrower"), the other "Credit Parties" from
time to time party to the Credit Agreement referred to below (together with the
Borrower, collectively, the "Credit Parties"), the financial institutions from
time to time party to such Credit Agreement (collectively, the "Lenders", and
each individually, a "Lender"), and General Electric Capital Corporation, as
the "Agent" for the Lenders (the "Agent").  Undefined capitalized terms which
are used herein shall have the meanings ascribed to such terms in the Credit
Agreement.

                                 WITNESSETH:


        WHEREAS, the Borrower, the other Credit Parties, the Lenders and the
Agent are parties to that certain Credit Agreement dated as of October 24, 1997,
as heretofore amended (the "Credit Agreement"), pursuant to which the Lenders
have agreed to provide, subject to the terms and conditions contained therein,
certain loans and other financial accommodations to the Borrower;

        WHEREAS, the Borrower failed to comply with the Minimum Net Worth
covenant as of December 31, 1997 and during the period after such date through
the effective date of this Agreement, as set forth in paragraph (e) of Annex G
of the Credit Agreement (hereinafter, collectively, the "Existing Default");

        WHEREAS, the Borrower has requested that the Lenders, and subject to
the terms and conditions of this Agreement the Lenders are willing to, (i)
waive the Existing Default and (ii) amend the Minimum Net Worth covenant for
the remaining period of the Credit Agreement.

        NOW, THEREFORE, in consideration of the foregoing premises, the terms
and conditions stated herein and other valuable consideration, the receipt and
sufficiency of which are hereby acknowledged by the Borrower, the Lenders and
the Agent, such parties hereby agree as follows:

        1.  Amendment.  Subject to Paragraph 3 of this Agreement, and effective
as of the date of this Agreement, the Credit Agreement is hereby amended to
delete the figure "$1,700,000" which appears in the definition of "Net Worth" in
Annex A of the Credit Agreement, and to replace such figure with the figure
"$3,850,000".

        2.  Waiver.  Subject to Paragraph 3 of this Agreement and effective as
of the date of this Agreement, each of the Lenders and the Agent hereby waives
the Existing Default.




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          3.  Effectiveness of this Agreement; Conditions Precedent. The
provisions of Paragraphs 1 and 2 shall be deemed to have become effective as of
the date of this Agreement, but such effectiveness shall be expressly
conditioned upon the Agent's receipt on or before April 15, 1998 of each of the
following:

          (a)  an originally-executed counterpart of this Agreement executed by
a duly authorized officer of the Borrower, each other Credit Party, and each of
the Requisite Lenders; and

          (b)  originally-executed counterparts to a Reaffirmation of Guaranties
duly executed by the Pegasus Funds substantially in the form attached hereto.

          4.  Representations and Warranties.  (a) The Borrower and each other
Credit Party hereby represents and warrants that this Agreement constitutes the
legal, valid and binding obligation of the Borrower and such other Credit Party
enforceable against the Borrower and each other Credit Party in accordance with
its terms.

          (b)  The Borrower and each other Credit Party hereby represents and
warrants that its execution and delivery of this Agreement, and its performance
hereafter of the Credit Agreement as modified by this Agreement, have been duly
authorized by all necessary corporate action, do not violate any provision of
its articles of incorporation, bylaws or other charter documents, will not
violate any law, regulation, court order or writ applicable to it, will not
require the approval or consent of any governmental agency, and do not require
the approval or consent of any third party under the terms of any contract or
agreement to which the Borrower, any other Credit Party, Parent or any
Subsidiary of the Borrower or any other Credit Party is bound.

          5.  Reference to and Effect on Credit Agreement.  The Credit Agreement
shall remain in full force and effect and is hereby ratified and confirmed.
Except as is expressly set forth in Paragraph 2 of this Agreement, neither the
execution, delivery nor effectiveness of this Agreement shall operate as a
waiver of any right, power or remedy of the Agent or any Lender of any Default
or Event of Default under the Credit Agreement, all of which the Agent and the
Lenders hereby expressly reserve.  The Borrower, each other Credit Party, the
Lenders and the Agent agree and acknowledge that this Agreement constitutes a
"Loan Document" under and as defined in the Credit Agreement.

          6.  Reaffirmation.  Each of the Borrower and the other Credit Parties
hereby (a) ratifies and reaffirms all of its payment and performance
obligations, contingent or otherwise, under each Loan Document to which it is a
party, (b) agrees and acknowledges that such ratification and reaffirmation is
not a condition to the continued effectiveness of such Loan Documents and (c)
agrees that neither such ratification and reaffirmation, nor the Agent's and the
Lenders' solicitation of such ratification and reaffirmation, constitutes a
course of dealing giving rise to any obligation or condition requiring a
ratification or reaffirmation of the Borrower's or the 



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other Credit Parties' obligations under the Loan Documents with respect to any
subsequent modifications to the Credit Agreement or other Loan Documents.

        7.  Governing Law.  This Agreement shall be governed by and construed
in accordance with the laws and decisions of the State of Illinois (including
S.H.A. 735 ILCS 105/5-1, et. seq., but without giving effect to any other
conflicts of law provisions).

        8.  Agent's Expenses.  The Borrower hereby agrees to promptly reimburse
the Agent for all of the reasonable out-of-pocket expenses, including, without
limitation, attorneys' and paralegals' fees, it has heretofore or hereafter
incurred or incurs in connection with the preparation, negotiation and execution
of this Agreement.

        9.  Counterparts.  This Agreement may be executed in counterparts, each
of which shall be an original and all of which together shall constitute one
and the same agreement among the parties.


                                   * * * *









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          IN WITNESS WHEREOF, this Agreement has been duly executed as of the
day and year first above written.



                                        CODE-ALARM, INC.


                                        By:  /s/ Craig S. Camalo
                                            ----------------------------------
                                            Name:  Craig S. Camalo
                                            Title: Vice President

                                        GENERAL ELECTRIC CAPITAL
                                        CORPORATION, as Agent and Lender

                                        
                                        By:  /s/ Catherine L. Midkiff 
                                            ---------------------------------- 
                                            Name: Catherine L. Midkiff
                                                  ----------------------------
                                            Title: Duly Authorized Signatory
                                                   ---------------------------

                                        TESSCO GROUP, INC.

                                        By:  /s/ Craig S. Camalo
                                            ---------------------------------- 
                                            Name: Craig S. Camalo       
                                                  ----------------------------
                                            Title: Secretary 
                                                   ---------------------------

                                        CHAPMAN SECURITY SYSTEMS, INC.


                                        By:  /s/ Craig S. Camalo
                                             ---------------------------------
                                             Name:  Craig S. Camalo      
                                                    -------------------------- 
                                             Title: Secretary
                                                    -------------------------- 





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                                        INTERCEPT SYSTEMS, INC.



                                        By:     /s/ Craig S. Camalo    
                                                -------------------------
                                                Name:  Craig S. Camalo 
                                                -------------------------
                                                Title: Secretary       
                                                -------------------------


                                        ANES, INC.

                                        By:     /s/ Craig S. Camalo    
                                                -------------------------
                                                Name:  Craig S. Camalo 
                                                -------------------------
                                                Title: Secretary       
                                                -------------------------





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                         REAFFIRMATION OF GUARANTIES


        Reference is hereby made to (i) that certain Limited Supplemental
Guaranty dated as of October 24, 1997 (the "Supplemental Guaranty") among
Pegasus Partners, L.P., a Delaware limited partnership, and Pegasus Related
Partners, L.P., a Delaware limited partnership (collectively, the
"Guarantors"), and General Electric Capital Corporation, a New York
corporation, individually and as agent (the "Agent"), (ii) that certain Limited
Litigation Guaranty dated as of October 24, 1997 (the "Litigation Guaranty")
among Guarantors and the Agent, (iii) that certain Credit Agreement
dated as of October 24, 1997, as heretofore amended (the "Credit Agreement"),
among Code-Alarm, Inc., a Michigan corporation (the "Borrower"), certain
other "Credit Parties" referred to and as defined therein (the "Credit
Parties"), certain "Lenders" from time to time party thereto (the "Lenders"),
and the Agent, and (iv) that certain Amendment No. 2 and Waiver No. 2 to Credit
Agreement of even date herewith (the "Amendment") among the Borrower, the
Credit Parties, the Lenders and the Agent.

        Each of the Guarantors hereby (a) acknowledges having received and
reviewed a copy of the Amendment, (b) ratifies and reaffirms all of its payment
and performance obligations, contingent or otherwise, under the Supplemental
Guaranty and the Litigation Guaranty (collectively, the "Guaranties"), (c)
agrees and acknowledges that such ratification and reaffirmation is not a
condition to the continued effectiveness of such Guaranties and (d) agrees
that, without limiting any of the express provisions of the Guaranties, neither
such ratification and reaffirmation, nor the Agent's and the Lenders'
solicitation of such ratification and reaffirmation, constitutes a course of
dealing giving rise to any obligation or condition requiring a ratification or
reaffirmation of the Guarantors' obligations under the Guaranties with respect
to any subsequent modifications to the Credit Agreement or other Loan
Documents.

        IN WITNESS WHEREOF, this instrument has been executed and delivered as
of this 8th day of April, 1998.


PEGASUS PARTNERS, L.P.                  PEGASUS RELATED PARTNERS, L.P.
By:  PEGASUS INVESTORS, L.P.,           By:  PEGASUS INVESTORS, L.P.,
     as Managing General Partner             as Managing General Partner
By:  PEGASUS INVESTORS GP, INC.,        By:  PEGASUS INVESTORS GP, INC.,
     as General Partner                      as General Partner





By:  /s/ Richard Cion                    By:  /s/ Richard Cion
    -----------------------------            -----------------------------
    Name:  Richard Cion                     Name:  Richard Cion
           ---------------------                   ----------------------
    Title: Vice President                   Title: Vice President
           ---------------------                   ----------------------