Store Loop MAPs
   The following store loop maintenance analysis procedures (MAPs) were written for the 4680 store system.  Since store loop operation is the same    for 4693, 4684, and 4683 terminals, they can be applied to either. 

   When reviewing these MAPs, the various models of terminals may be 
   interchanged according to the following chart: 
          4684-XXX may also be 4693-541 
          4683-XX1 may also be 4693-421 or 4693-321 
          4683-X02 may also be 4693-202 
   This section contains information that can be used to learn more about the  store loop and its failure modes. 
   °   The following full-page figures represent a typical store loop, using 
       the IBM loop wiring concentrator. 
   °   Each figure represents the same store loop, each with the following 
       conditions: 
Store loop with an open condition in the top loop wiring concentrator.

           Store loop with the primary store controller offline.

Store loop with an open condition in bottom loop wiring concentrator. 

Store loop with a failing point-of-sale terminal. 

   °   Your store loop may not be wired like this, but the position of your 4683s on the loop and the relationship to the store controller is similar. 

   °   The 4683-P can also be a 4683-001 or 4683-A01.  The 4683-002 can also be a 4683-A02. 

   °   The terminal numbers are shown in numeric order, but they can be put in any order on your store loop.

   °   The store controller transmits data to the first 4683 down-loop on the store loop.  This 4683 receives the data and passes it to the next 4683 down-loop.  This continues with each 4683 receiving data from the 4683 immediately up-loop from its position, and passing it on to the next 4683 down-loop.  The last 4683 down-loop passes the data back to the store controller.