6.   INTERACTION PROTOCOL


6.01   This  section defines  maintenance sub-system  interaction
protocol and man-machine protocol.  Refer to Figure 6-1.


MAINTENANCE SUB-SYSTEM INTERACTION PROTOCOL (MSIP)


6.02   MSIP  is initiated by a  detection of a fault  (FD).  When
the I/O  system, alarm  detection SS, or  any of  the maintenance
sub-systems, detect a fault, the  maintenance sub-system in whose
area the problem  falls, is responsible for  running a diagnostic
rocedure. Should the  diagnosis be sucessful and  the problem is
not transient, then  an error message is sent to  the routing and
reporting SS.  Should the diagnosis fail, a diagnostic message is
sent to the routing and reporting SS.  The maintenance sub-system
is capable  of initiating  an action  when it  can determine  the
cause  of  the  failure.   If so,  an  action  message  (followed
possibly  by  a  status  message) is  sent  to  the  routing  and
reporting SS.









               (c)  NORTHERN TELECOM LIMITED, 1978
                 MAINTENANCE SYSTEM DMS-100/200








                        NTP 297-1001-106                  PAGE 13
                       PREL., ISSUE 01D01
                          May 25, 1978



6.03   MSIP as initiated by a manual request (MR) from the VDU.
Three types of messages can be requested by the VDU:

     (a)  Action request  (AR) -  which  may result  in a  status
         change and hence a status update on the VDU.

     (b) Status  request (SR)  - which  is a  simple request  for
         information.

     (c) Diagnostic request  (DR) - which is a  simple request to
         run a diagnostic.   No action is taken as  a function of
         the result of the diagnosis  when the request comes from
         the MAP.


MAN-MACHINE PROTOCOL


6.04   Refer to Figure 6-2.   Having  observed a status change on
the system  VDU display,  the maintenance  personnel can  request
sublevel information, showing overall sub-system status.  Further
information  is   retrievable  from  the  logging   mechanism  on
diagnostic, error and  status messages stored therein.   Based on
this  information  the  fault is  repaired  and  the  maintenance
personnel then request that the component be returned to service.
This  request  results  in  a  diagnostic  being  run,  which  if
successful, then  performs the action  of returning  the repaired
component to service.  The associated  action and status messages
are also  generated at  this time.   If  the diagnostic  fails, a
diagnostic  message is  sent  resulting in  a  repetition of  the
repair attempt  and a  re-run of the  diagnostic. The  fault will
continue to  be displayed  as an alarm  on the  VDU, even  if the
audible alarm is off, until the diagnostic is successful.