ABB S800 Product Manual page 64

Module Termination Unit
Compact and Intrinsic Safety MTUs are 58mm (2.3") wide, Extended MTUs are
120mm (4.72") wide and Redundant MTUs are 124 mm (4.88") wide. The MTU
types can be mixed and matched within an I/O station to fit a user's needs. Choice of
MTU type can be made freely, trading space versus termination needs.
MTUs are available with rated insulation voltages 50 V and 250 V. The 50 V types
can be used with all 24/48 V discrete I/O and analog I/O modules. The MTUs with
250 V rated insulation voltage are used with all 120 V and 250 V rated I/O modules.
An inserted I/O module is assigned the unique position identity of its MTU.
Through the incremental bus design the physical size of an S800 I/O installation is
directly proportional to the number of installed MTUs.
The S800 I/O modules can be inserted and removed from MTUs without
disturbing system operation.
The physical lock for S800 I/O which locks an I/O module to its MTU allows I/O
module removal only when the lock is in its unlocked position. The locking
mechanism also acts as a logic lock so that an I/O module is operable only when the
lock is in the locked position. If the lock is in its unlocked position, output channels
are de-energized and I/O modules can be inserted/removed without the need to
remove system or field power.
64
Section 2 Product Description
3BSE015969-600 A