ARS 101


ARS Demonstration

A user wants to dial off the phone system to a public telephone number, 415-555-1212.  If we assume that a user must dial 9 to reach an outside line, then the call processing looks like this (User dials 9-1415-555-1212):

We’re going to assume that the calling phone set has an NCOS of 5.  This information is relevant towards the end of the process.

You can verify that 9 is AC1 (Access Code 1) by printing all of your DNB table in LD 20 and looking for the TYPE NARS entries.  AC1 is BARS, AC2 is NARS.  More on NARS later in the ARS 201 and ARS 301 tutorials.  You can also review and configure the AC1 and AC2 codes in LD 86, but we’ll cover that in ARS 201.

Since 9 is identified as the AC1 code, the Primary Translator hands off to the AC1 Translator.  In simplified terms, this means that the Primary Translator strips the 9 from the digits dialed and the remaining digits are interpreted by the AC1 Translator.

As the user continues to dial 1415, the AC1 Translator identifies 1415 as an NPA and performs a lookup on that NPA.

NPA 1415 points to RLI 1 (Route List Index) after the expected number of digits are dialed.

Since the Translator identifies 1415 as the NPA, the expected number of digits is then set to 7.  (Meaning that after the user dials 9-1415- the system expects 7 more digits before the number will be processed.)  Other codes (NXX or SPN) have different length expectations, these codes, SDRR (the DENY 976 seen above) and Timeout Handling (what happens if, while dialing, the user pauses too long before dialing the expected number of digits) will be discussed in greater detail in the following pages.


The user continues to dial -555-1212, the AC1 Translator recognizes the completion on the NPA pattern and selects the configured RLI (1) for call completion.  ARS evaluates each entry in RLI 1 in sequence to determine if the call can complete.


Simply speaking (at least for this tutorial) the call is looking for two things, (1) Does the user have sufficient rights to access this entry, meaning is the NCOS on their phone configured with an FRL that exceeds the FRL on the entry, (2) Are there idle channels on the route.  If both conditions are met (there are other conditions that will be covered in ARS 201 and 301) then digit manipulation is evaluated (DMI 0, no digit manipulation) and the final digits are delivered to route (ROUT) 2.

If either condition is not met, then the next entry (if any) is evaluated.  If there are no entries remaining, then REOR (reorder) is offered to the calling party.

Step 1 of the RLI evaluation process is to determine if the calling phoneset has an NCOS with an FRL that exceeds the FRL configured on the ENTR.  At the beginning, we assume we would have an NCOS of 5.  Looking up NCOS 5 (more on the NCTL table in the following pages), we find that NCOS 5 is set to FRL 5.  Since the FRL configured on NCOS 5 is greater than or equal to the FRL on the ENTR, the call is permitted.

Step 2 in the evaluation process is to determine if there are any idle channels on the route.  In this case, we’re going to assume there are sufficient number of idle channels to complete the call…

…and the call completes.

If a digit manipulation index (DMI) were configured on the ENTR, then the DMI would be applied prior to delivering the call to the ROUT.  In this case, the DMI is set to zero (0), meaning no digit manipulation.