Allied Telesis AT-MC104ST/FS3, FS4 - Manual (Page 14)

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MissingLink. The MissingLink feature activates the fiber optic ports on the
media converter to pass the “Link” status of their connections to each other.
When the media converter detects a problem with one of the ports, such as the
loss of connection to a node, the media converter shuts down the connection to
the other port, thus notifying the node that the connection has been lost.
For example, if the fiber optic cable connected to the multimode port on the
media converter were to fail, the unit would respond by dropping the link on
the single-mode port. In this way, the media converter notifies the end node
connected to the single-mode port that the connection on the other port has
been lost. If the failure had started on the single-mode port, the unit would drop
the connection to the multimode port.
The value to this type of network monitoring and fault notification is that some
hubs and switches can be configured to take a specific action in the event of the
loss of connection on a port. In some cases, the unit can be configured to seek a
redundant path to a disconnected node or send out a trap to a network
management station, and so alert the network administrator of the problem.
Note
The MissingLink feature is disabled when you perform a link test.
Consequently, to ensure that the MissingLink feature is enabled on the
media converter, always set the Link Test/MissingLink button to the
M/L ON (IN) position during normal network operations.
External AC/DC Power Adapter
The power adapter supplies 12 volts DC to the media converter. Allied Telesyn
supplies an approved safety compliant AC power adapter for the 120 and 240
V AC versions with an unregulated output of 12 VDC at 1A.
Figure 2 External AC/DC Power Adapter (North American version)