How to detect a low reception level on the ISD400 Core data transmission system?

To ensure uninterrupted data transmission, the ISD400 Core data transmission system requires a sufficient reception level. If not, the error rate in the telegrams increases. In the worst case, transmission may even stop completely.

With ISD400 Core (type code ISD400-1xxx or ISD400-6xxx), the reception level can be read off the bar graph on the display in RUN mode. In addition, the orange frontside status LED is permanently active if the reception level is sufficient. If the reception level falls below the warning threshold (e.g. due to poor alignment or dirt), data transmission up to that point is retained. The received signal continues to be shown as a bar graph on the display. However, the status LED switches to flashing mode. This flashing remains even if the reception level falls below the function threshold. In this case, however, data transmission is interrupted and “NoSync” is shown on the display instead of the bar graph.

Note:

The change from sufficient reception level to the function reserve described earlier cannot be detected remotely via the evaluation of switching output Q (pin 2). This output is purely an error but no warning output. It is therefore active (low signal) when the reception level falls below the function threshold, which causes the data transmission to stop.