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The system used is the Foxboro system: the requirement is to obtain signals from the existing toxic gas detectors; whenever one of these detectors triggers an alarm, a digital signal is sent to the audible and visual alarm device on site to initiate an alarm. (What should be done if there are 20 toxic gas alarms and 4 audible and visual alarms?)
Do you mean that if any one of the 20 signals triggers an alarm, all 4 audible and visual alarms at the site will sound? If so, two CALCA blocks and 4 cout blocks will suffice. One CALCA has 16 BIs; the HAI parameters connecting to the AI alarm points are passed, and then the BO is output to the BIs of the second CALCA. Then connect to COUT’s IN via BO
It is possible to configure internally 5 signals to be fed into a comparison block; when the threshold value is exceeded, an analog switch value is output through an output block. I have not used Foxboro’s systems before, so I’m not sure if this can be achieved in that way.