5.18.2.3. Trunk - SIU Connection 
As the general description clearly indicates, there must be an MFX-R2
transmitter/receiver pair assigned to a trunk during the exchange of
signals. The configuration in TACSU is responsible for the correct connection:
MFCVAR=x, DIALTYPE=MFC-MFC.
MFCVAR in this AMO corresponds to the MFCVAR in the AMO MFCTA (described
later).