<PAGE>   1
                                                                   EXHIBIT 10.1

                               AMENDMENT NO. 1 TO
                                CREDIT AGREEMENT

       THIS AMENDMENT AGREEMENT is made and entered into this 21st day of
March, 2000, by and among SENSORMATIC ELECTRONICS CORPORATION, a Florida
corporation (herein called the "Parent"), the BORROWING SUBSIDIARIES parties
hereto, if any (the Parent and each Borrowing Subsidiary is individually
referred to as a "Borrower" and collectively as the "Borrowers"), BANK OF
AMERICA, N.A. (the "Administrative Agent"), as Administrative Agent for the
lenders (the "Lenders") party to a Credit Agreement dated December 9, 1999 among
such Lenders, the Parent and the Administrative Agent, as amended (the
"Agreement") and a new Lender party to this Amendment Agreement (the "New
Lender").

                              W I T N E S S E T H:

         WHEREAS, the Parent, the Agent and the Lenders have entered into the
Agreement pursuant to which the Lenders have agreed to make revolving loans to
the Borrowers in the principal amount of $115,000,000 as evidenced by the Notes
(as defined in the Agreement); and

         WHEREAS, the New Lender has agreed to provide to the Borrowers Loans
and participations in Letters of Credit of up to $15,000,000, $5,000,000 of
which shall be by an assignment pursuant to SECTION 12.1 of the Agreement and
$10,000,00 of which shall increase the Total Revolving Credit Commitment to
$125,000,000 and the parties hereto desire to amend the Agreement in the manner
herein set forth effective as of the date hereof;

         NOW, THEREFORE, the Borrower, the Administrative Agent and the New
Lender do hereby agree as follows:

         1. DEFINITIONS. The term "Agreement" as used herein and in the Loan
Documents (as defined in the Agreement) shall mean the Agreement as hereby
amended and modified. Unless the context otherwise requires, all terms used
herein without definition shall have the definition provided therefor in the
Agreement.

         2. AMENDMENTS. Subject to the conditions hereof, the Agreement is
hereby amended, effective as of the date hereof, by deleting EXHIBIT A and
inserting in lieu thereof EXHIBIT A attached hereto, and the New Lender agrees
by the execution of this Amendment Agreement that it shall be a party to the
Agreement as a "Lender" and shall provide to the Borrower its Revolving Credit
Commitment in the amount set forth in EXHIBIT A attached hereto.

         3. REPRESENTATIONS AND WARRANTIES. Each Borrower hereby certifies that:



                                       1
<PAGE>   2




                  (a) The representations and warranties made by Borrower in
         ARTICLE VII thereof are true in all material respects on and as of the
         date hereof except to the extent that such representations and
         warranties expressly relate to an earlier date and except that the
         financial statements referred to in SECTION 7.6(a) shall be those most
         recently furnished to each Lender pursuant to SECTION 8.1(a) and (b);

                  (b) There has been no material adverse change in the
         condition, financial or otherwise, of the Parent and its Material
         Subsidiaries since the date of the most recent financial reports of the
         Parent received by each Lender under SECTION 7.6(A), or if more recent,
         those received under SECTION 8.1 thereof, other than changes in the
         ordinary course of business, none of which has been a material adverse
         change; and

                  (c) No event has occurred and no condition exists which, upon
         the consummation of the transaction contemplated hereby, constituted a
         Default or an Event of Default on the part of the Borrower under the
         Agreement or the Notes either immediately or with the lapse of time or
         the giving of notice, or both.

         4. CONDITIONS. As a condition to the effectiveness of this Amendment
Agreement, the Borrower shall deliver, or cause to be delivered to the
Administrative Agent, the following:

                  (a) Four (4) executed counterparts of this Amendment
         Agreement; and

                  (b) A fully-executed Revolving Note and Competitive Bid Note
         payable to the Lender in the amount of Lender's Revolving Credit
         Commitment.

         5. OTHER DOCUMENTS. All instruments and documents incident to the
consummation of the transactions contemplated hereby shall be satisfactory in
form and substance to the Administrative Agent and its counsel; the
Administrative Agent shall have received copies of all additional agreements,
instruments and documents which it may reasonably request in connection
therewith, including evidence of the authority of Borrower to enter into the
transactions contemplated by this Amendment Agreement, in each case such
documents, when appropriate, to be certified by appropriate corporate or
governmental authorities; and all proceedings of the Borrower relating to the
matters provided for herein shall be satisfactory to the Administrative Agent
and its counsel.

         6. ENTIRE AGREEMENT. This Amendment Agreement sets forth the entire
understanding and agreement of the parties hereto in relation to the subject
matter hereof and supersedes any prior negotiations and agreements among the
parties relative to such subject matter. No promise, conditions, representation
or warranty, express or implied, not herein set forth shall bind any party
hereto, and no one of them has relied on any such promise, condition,
representation or warranty. Each of the parties hereto acknowledges that, except
as in this Amendment Agreement or otherwise expressly stated, no
representations, warranties or commitments, express or implied, have been made
by any other party to the other. None of the terms of conditions of this
Amendment Agreement may be changed, modified, waived or canceled orally or
otherwise, except by writing, signed by all the parties hereto, specifying such
change, modification, waiver or cancellation of such terms or conditions, or of
any proceeding or succeeding breach thereof.



                                       2
<PAGE>   3


         7. FULL FORCE AND EFFECT OF AGREEMENT. Except as hereby specifically
amended, modified or supplemented, the Agreement and all of the other Loan
Documents are hereby confirmed and ratified in all respects and shall remain in
full force and effect according to their respective terms.

                  [Remainder of page intentionally left blank.]



                                       3
<PAGE>   4


         IN WITNESS WHEREOF, the parties hereto have caused this Amendment
agreement to be duly executed by their duly authorized officers, all as of the
day and year first above written.

                                            SENSORMATIC ELECTRONICS CORPORATION

WITNESS:

illegible                                   By:     /s/ THOMAS F. DONAHUE
----------------------------                    -------------------------------
                                                     Name:    Thomas F. Donahue
illegible                                   Title:   Vice President & Treasurer
----------------------------


                                       4
<PAGE>   5


                                   BANK OF AMERICA, N.A., as Administrative
                                   Agent

                                   By: /s/ RICHARD M. STARKE
                                      -------------------------------------
                                   Name:    Richard M. Starke
                                   Title:   Managing Director



                                       5
<PAGE>   6


                                   BANKATLANTIC

                                   By:   /s/ ANA C. BOLDUC
                                      ----------------------------
                                   Name:    Ana C. Bolduc
                                   Title:   Senior Vice President



                                       6
<PAGE>   7


                                    EXHIBIT A

                        Applicable Commitment Percentages

                                                                   APPLICABLE
                                           REVOLVING CREDIT        COMMITMENT
LENDER                                        COMMITMENT           PERCENTAGE
------                                     -----------------       ----------

Bank of America, N.A                         $ 25,000,000               20%

SunTrust Bank, South Florida, N.A            $ 25,000,000               20%

Bank One, N.A. (Chicago Main Office)         $ 25,000,000               20%

BankBoston, N.A                              $ 20,000,000               16%

Dresdner Bank Lateinamerika AG,
Miami Agency                                 $ 15,000,000               12%

BankAtlantic                                 $ 15,000,000               12%
                                             ------------              ---

                                             $125,000,000              100%
                                             ============              ===




                                       7