EXHIBITS Exhibit No. Description 1 Joint Filing Agreement dated as of December 20, 2000, by and between Parent and the Purchaser.

EXHIBITS

     Exhibit No.           Description

         1                 Joint Filing Agreement dated as of December 20,
                           2000, by and between Parent and the Purchaser.


                                                                   Exhibit No. 1

                             JOINT FILING AGREEMENT

         In accordance with Rule 13d-1(k) under the Securities Exchange Act of
1934, as amended, the persons named below each hereby agrees that the Schedule
13D filed herewith and any amendments thereto relating to the acquisition of
shares of Common Stock of Detection Systems, Inc. is filed jointly on behalf of
such person.

Dated:   December 20, 2000

                                           ▇▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇▇

                                           By:   /s/ ▇▇▇▇▇ ▇▇▇▇▇
                                           ------------------------------------
                                           Name:     ▇▇▇▇▇ ▇▇▇▇▇
                                           Title:    Senior Vice President

                                           By:   /s/ Dr. Heiko ▇▇▇▇▇▇
                                           ------------------------------------
                                           Name:     Dr. Heiko ▇▇▇▇▇▇
                                           Title:    Senior Legal Counsel

                                           BOSCH SECURITY SYSTEMS CORPORATION

                                           By:   /s/ ▇▇▇▇ ▇▇▇▇▇▇▇▇
                                           ------------------------------------
                                           Name:     ▇▇▇▇ ▇▇▇▇▇▇▇▇
                                                     Title: President

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