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The primary function of the MDD-4490 is to raise an
alarm if its input MPEG Transport Stream fails. Its
secondary function is to raise an alarm if the
Transport Stream is not the correct stream as
identified by its Stream Id. Thirdly it can raise an
alarm if a particular program number is missing from
the stream and in addition monitors a number of the
parameters of first priority measurements of ETR290.
There are 5 green status LEDs named PAT, SID,
PMT, PGM and PCR. These five should be
illuminated in the presence of a valid Transport
Stream. 204 is another green LED that lights when
the input signal is a 204 byte packet length signal.
CNT is an amber LED and lights on a Continuity
Count error. ASI is red and indicates a failure of the
Transport Stream.
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There are two relays whose contacts are available on
the rear assembly. They are labelled Urgent and Non-
Urgent. If the Urgent relay operates then the red
URG led on the front panel will light. If the Non-
Urgent relay operates then the amber led NON will
light. Each of the relays can be selected (by dip
switches) to operate on any or all of the error states
of any of the seven status LEDs.
Simple Network Management Protocol (SNMP)
monitoring is possible if mounted in IRT's 4000
series frame fitted with SNMP capability.
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