| 摘要 |
In an input stage 10 for supplying electric status signals from a signalling arrangement 14 to a monitoring processor 12 in a security system, said signalling arrangement is connected to the input stage by means of an in-line to a connection input and an out-line from a connection output, and comprises a switch 51, 52 which can interconnect the lines, if appropriate via a diode D1, the input stage including: an output arrangement L1 for generating under the control of said processor a first binary output signal at a first output P1 and a secondary binary output signal at a second output P2; an input arrangement L2 for receiving and supplying to said processor a first binary input signal C at a first input I1 and a secondary binary input signal D at a second input 12; the first output P1 being electrically connected to the in-line and to the first input I1; the second output P2 being electrically connected to the out-line and to the second input I2, and the output arrangement L1 being capable of accepting all four permutations of first and second binary signals A, B, the processor 12 determining the status of the switch S1, S2 and being capable of detecting all faults in the lines and the input stage from the combinations of the first and second binary input signals C, D. <IMAGE> |
