Schellebelle has an older signal lay-out. Previously often used, but now-a-days abandon.
Typical is the suspension of the exit signal in the main track. While the exit signal for the siding is mostly a simplified main signal but not mandatory.
The "all clear" for the main track is given directly by the entry-signal.
a) Basic layout
b) A train is signalled through Schellebelle. "All clear" by the entry-signal
C) A train may depart the siding in the direction of Gent
More pictures can be found at http://www.l2527.be/fkr.htm
A similar situation can be found in the station of Neufchateau (still existing), Neufville (still existing)
or the old signal lay-out of Ezemaal (1996)
Ezemaal L36, old track layout. Signal direction from Leuven to Liege.