The four Miscellaneous Discrete Outputs (MDOs) can be used to drive signalling devices
or to influence the behavior of equipment external to the system. Each GPIO for the
MDO interfaces with a relay driver which controls a mechanical relay. All MDOs have
their common, normally closed (C) and normally open (O) contacts brought to the
Sub-D connector. ormally it is the non-energized state of the relay which is shown in the
figures. When GPIO becomes active, the relay is energized and the MDO output is
activated.
The MDOs shall float with respect to system ground.
An active MDO shall behave as a voltage free resistance of less than 10 Ω between the
output connection and its associated return. It shall be capable of carrying currents of not
more than 0.5 A. An inactive MDO shall behave as a voltage free resistance of more than
500 kΩ between the output connection and its associated return. It shall be capable of
withstanding voltages of not more than 72 VDC.
The MDO contacts shall be capable of sustaining the product of above mentioned current
and voltage during transitions.
The easy MDI contacts of the system do not need external power to function. The system
can detect a passive open or closed loop.
In case of accidental wrong usage of a non floating MDI, the system can withstand
without damage a permanent high input voltage between input and ground of; -72V to
+72V.
Figure 4-9 MDI implementation
System cabling
External cable installation
MDI/MDO interface
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365-313-103R8.0
Issue 2
July 2009
Alcatel-Lucent – Internal
Proprietary – Use pursuant to Company instruction
4-11
