5.26.5.5. External Clock Box (AECB, AICB, etc.) for OpenScape 4000 
The MCM module on the cPCI controller features a port for an external
clock box where an AICB, AECB or SASE can be connected. It should be
noted that this interface corresponds mechanically and electrically to
that of the MTSCG.
The external clock box must be configured as "AECB" using the AMO
REFTA for inclusion in network management.