5.18.3.3.1. Generation Notes on A Station Identification (Before the B Number) 
In this application, identification is performed on each incoming
call. The advantage of this method is that the dangerous time between
the "preliminary seizure" of the B station and ringing is short. The
disadvantage of this method is that the SIU MFC devices for both the
OpenScape 4000 and in the central office remain seized (considerably)
longer for each seizure.
You should perform the following generations using MFCTA (MFC parameter:
IDBEFBS) and FEASU so that the central office retrieves the A station
number:
FEASU: TRACCO = YES CHANGE-MFCTA:MFCVAR=x,TYPE=MFCVAR,OPT=MISC, PAR=IDBEFBS;
IMPORTANT:
In a concrete case, you must repeat and chain all parameters that have
already been set with '&'. The above example only sets the parameter IDBEFBS.