Configured dual processor architecture 

In centralized SPC, dual processor architecture can be configured to operate in following one of three modes:

1.  Standby mode: In this mode, one processor is active and the other one is on standby, both software and hardware wise.  The standby processor brought online when active processor fails.  A significant requirement of this configuration is ability of standby processor to reconstitute state of the exchange system when it takes over the control.

2.  Synchronous duplex mode: In synchronous duplex mode, hardware coupling is provided between two processors that execute the same set of instructions and compare results continuously. If a mismatch takes place, faculty processor is identified and taken out of service immediately. When system is operating normally,  two  processors  have  the  same  data  in  their  memories  at  all  the times and receive all information from exchangeenvironment.

3.  Load  Sharing  mode; In  load  sharing  operation,  an  incoming  call  is  assigned randomly  or  in  a  predetermined  order  to  one  of  the  processors  which  then handles  call  right  through  completion.  Hence both processors are active simultaneously and share the load and resources dynamically.