| 摘要 |
The invention relates to a method of random coding and its implementation for the protection of links in the face of sophisticated means of fraud, especially in remote surveillance. The device comprises a plurality of coder/sensor assemblies (1) which cannot be dismantled generating, on a two-wire line (2), a random PCM train obtained by parity (3) between a complex periodic function (4) and a random series (5) affected by the state of the said sensors (6). A programming device (7) allows transmission in continuous or erratic sequential mode. A switched resistor provides PCM modulation (8). A management unit (9) slaved to a drive circuit (10) controls the two-wire line, sends out the clock signals, extracts the defect information from the PCM code and enables alarms as a consequence (11). <IMAGE>
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