| 摘要 |
A data acquisition system, e.g. for an intrusion alarm system, has a plurality of distributed sensors 3 connected in sets to nodal units or concentrators 2. The concentrators are interrogated by clock pulses broadcast on a line 6 from a central control unit l and when each concentrator's address is reached it transmits back to the central unit over a line 7 a set of pulse signals the widths of which represent the voltage levels of the respective sensors 3 connected to it. Analogue sensor outputs may thus be transmitted. The sensor outputs are also preferably integrated at the concentrators 2, prior to pulse-conversion, over a period corresponding to a complete cycle of the local mains supply, thus to eliminate any mains interference. |
