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                           DATUM INC. AND SUBSIDIARIES

                                   EXHIBIT 21



                              LIST OF SUBSIDIARIES



                                                              State or Other
                                                              Jurisdiction of
         Name                                                 Incorporation
         ----                                                 -------------
                                                           
         Frequency and Time Systems, Inc.                     Delaware

         Austron, Inc.                                        Texas

         Efratom Time & Frequency Products, Inc.              Colorado

         Datum GmbH                                           Germany