I sometimes use network signals to "close" stations with a signal, rather than closing the station itself
Now i dont like the visibility of signals from further away, so i thought i put some lights next to them and let them shine
However, the signal cant read and write the "closed" condition at the same time, when switched by the circuit condition
Yet it can, when it´s just switched to red by a train on the track.
I have tested this by putting a block signal right in front of it, and its doing its job.
I have also tested by connecting the signal to a power pole to read whats sent. Its only sending the open signal, unless, again, its "closed" by a train on the track.
The open condition is sent to the pole (and network)
The loco in the picture is facing the wrong way, i just put it there manually to simulate a train waiting and "closing" the station that way.
I found this on my laptop while snoring away the nightshift at work, if absolutley needed i´ll search for the damn log file (there is no file with that name, that i can see

Signal green, working as intended Signal red, switched by circuit Signal red, switched by train on the track