Distant-only signals are signals that are not home signals (regular or switching) but conveying signal indications about a signal further down the road. They are either repeaters or first-time distant-only signals depending on how many blocks were signaled as cleared at the previous home signal.
Distant-only signals are not shown on the dispatcher’s desk, but are very important for the trains running on the scene. Their position on the territory impact the behavior of the train on when and how they accelerate or brake as follows:
If a train passes a regular home signal, the indication passed to the driver may have some information of status of the next signal(s) ahead of him. Or it may not, in which case the driver has to assume the next signal shows “stop” (he knows though how far away it is). The driver will keep this in mind and proceed with the appropriate speed until the train is close enough to the next signal for an update of the signal situation. If there is a distant-only signal on the way, the driver can get an update a little bit earlier – as if he got that information from the previous regular signal, but only as much as the previous signal could have shown. This includes the case where the previous signal did not show the status of the upcoming signal, in which case the distant-only signal is a “first-timer” and shows just if the next block cleared or not (and also possible speed restriction).
Distant-only signals never extend the number of blocks signaled from the previous home signal (considering 1-block signals as 2-block signal with the 2nd signal indicating “stop”). They can also be inactive for certain routes, e.g. if the distance to the next home signal is too large to be deemed necessary for those routes.
Distant-only signals can have trigger function assigned, and can also be located at an entrance of a block.