ported from 1.7.6 (#322)

Author: mvladic

src/bb3/dib-dcp405/dib-dcp405.cpp

@@ -1000,6 +1000,11 @@ struct DcpChannel : public Channel {
     }
 
     bool isErrorInputVoltageDetectedWhenChannellIsOff() override {
+        if (channel_dispatcher::getCouplingType() == channel_dispatcher::COUPLING_TYPE_SERIES) {
+            auto otherChannelIndex = channelIndex == 0 ? 1 : 0;
+            auto &otherChannel = Channel::get(otherChannelIndex);
+            return u.mon + otherChannel.u.mon > ERROR_INPUT_VOLTAGE_WHEN_CHANNEL_IS_OFF;
+        }
         return u.mon > ERROR_INPUT_VOLTAGE_WHEN_CHANNEL_IS_OFF;
     }    
 };