| 摘要 |
For transmission of alarm indication signals, in particular alarm signals from a message generator (1) via a transmission channel (5, 7, 9) to a message receiver (3), indication signals generated by indication signal generators (11) are transmitted together with identification signals which are generated by an identification signal generator (21, 27) of the message generator (1). The message receiver (3) evaluates both the message signals and the identification signals. The message generator (3) also has an identification signal generator (25, 31) and, like the identification signal generator (21, 27) on the message generator side, transmits a plurality of different identification signals via the transmission channel (5, 7, 9). On receiving each of the identification signals of the identification signal generator (25, 31) on the message receiver side, the identification signal generator (21, 27) on the message generator side transmits an identification signal constantly allocated to the received identification signal. A random generator (29) controls the temporal succession of the different identification signals transmitted by the identification signal generator (25, 31) on the message receiver side in randomised fashion. This renders the alarm indication system, particularly one using public telephone lines as a transmission channel, more secure against tampering. <IMAGE>
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