Conference 7.286::fddi

>    But the basic question, how does the OBR port work?

To see what the OBR does to a network see Raj Jain's "Fddi Handbook",
5.8 Optical Bypasses.

To see what is the pinout of the OBR port see note 1940.*.

The "insert" and "deinsert" actions are initiated by FDDI Station 
Management (SMT) funtion Entity Coordination Management (ECM).

   SM_PM_BYPASS.request (Control_Action)

   This primitive is generated by SMT and asserted to PMD to indicate that
   SMT wants to join or leave the FDDI network.

   The Control_Action parameter shall include the following: Insert,
   Deinsert.

   When Generated:
   SMT shall generate this primitive whenever it wants to activate or
   deactivate the optical switch(es).

   Effect Upon Receipt:
   Upon receipt of this primitive with a Control_Action of Insert, PMD
   activates the optical switch such that the MIC inbound optical signal
   from the cable plant is directed to the optical receiver. The output of
   the optical transmitter shall be directed to the MIC output to the
   cable plant.

   Upon receipt of this primitive with a Control_Action of Deinsert, PMD
   deactivates the optical swithc such that the MIC inbound optical signal
   from the cable plant is directed through the switch to the MIC output
   to the cable plant. The output of the optical transmitter shall be
   directed through the optical switch to the input of the optical
   receiver. This state is called the bypass mode.

Throughout this notes conference you will see the use of OBRs discouraged.
See note 320.*. Consequently, the actual OBR function itself is not tested
by day-to-day use.  I know of several implementations where the OBR
will work only if the OBR is present when the device is powered on.

That said, you could always just try monitoring a real OBR and see if the
signal (Pins 1,2 high; Pins 3,4 low) gives you the the indication that the
customer wants.

Regards,
Chuck

    
    
    Thanks for the information in .1, but the real question is how does the
    OBR PORT on the DECconcentrator work?
    
    What pins are active, or what makes them active?
    
    The other OBR notes describe the pins, but not the status, or
    functions.
    
    What causes the OBR to operate, loss of a mod PMD or only total loss?
    
    The PPT (Carrier) wants to use the OBR for alarming, and they would
    like to monitor pins X and Y and loss of signal means the box is dead
    etc.
    
    
    thanks
    
    Mark. 

    Mark, it looks to me like all your carrier has to do is
    monitor either pins 1 or 2 relative to either pins 3 or 4.
    Pins 1 & 2 are a positive dc voltage (+5v), and pins 3 & 4
    are a negative dc voltage (gnd). Whenever the module powers off
    pins 1 & 2 will not be positive relative to pins 3 & 4.
    The pins 1 & 2 are used to energize the 2 optical switches in
    an optical bypass relay (for both the primary and secondary FDDI
    rings. Pins 3 & 4 are the gnd returns for pins 1 & 2 respectively.
    So take your pick, monitor the  pin 1 & 3 pair or monitor the 
    pin 2 & 4 pair. For the purpose your carrier is accomplishing the
    other pins can be ignored. 
    
    Bob
    

    Hi Bob,
    
    
    Thanks