This is part six of what I've called "Nortel for Dummies." So far we've copied a phone and made some important changes to it. Now it's time to talk about getting a call out of your PBX.
I'm sure some systems still allow users to dial an access code to get dial tone without first screening the number dialed, but most systems are set to first look at the number, then decide how (or whether) it will be sent out. In the Nortel PBXs this screening process is called BARS (Basic Automatic Route Selection).
What do you dial first in your system when you want to make a long-distance call? That is probably the BARS Access Code or AC1. Let's take a quick look at how a long-distance call is processed by BARS.
Choose a long-distance call you might make in the system and note the digits. I'll use dial patterns common in the US, so understand that it will be different in most other countries. The first digit or digits will be the BARS Access Code, often 9. After that will probably be four digits, beginning with 1, and followed by an Area Code. These four digits are called NPA.
Log into the system and load overlay 90. REQ: prt CUST: FEAT: net TRAN: ac1 TYPE: npa NPA: 1291 - Enter the NPA from your long distance selection here
The result will begin with the RLI (Route List Index) that will process the call. Some supplemental information may also appear as exceptions. When the digit or digits that follow the NPA match these exceptions, the call will either be rejected (DENY) or routed as an internal call (LDID) or routed in any of several other less-common ways. Since you chose a long-distance call, it probably will be sent to a RLI. Let's assume it's RLI 7 and follow it another step.
Exit the overlay with **** and load overlay 86.
REQ: prt
CUST:
TYPE: rlb
RLI: 7
ENTRY: Press
Look over the printout making note of how many times you see the prompt: ENTRY. It may have only one, or it may have many. Each one of these entries will give the call an opportunity to match its conditions. The first one that matches will be the one to send the call out. If there are no matches, the call will not complete.
For the first entry, look at the LTER prompt. A "yes" here means the number is simply dialed as an internal call. This long distance call will have "no" here.
The next prompt will be ROUT. The number here is the trunk route to handle the call if the other conditions are met. Your system may have only one trunk route that is used for all incoming and outgoing calls, or it may have many different routes, each with a different purpose or destination. Perhaps this route is dedicated for long-distance calls through a long-distance provider.
There are several less-common controls that follow including time-of-day controls, but the next prompt most people need is FRL (Facility Restriction Level). The number that follows is a minimum number required for the call to complete in this entry. Most companies make the FRL value the same as the NCOS (Network Class Of Service) on stations, so in most cases a dialing station must have at least as great an NCOS as the FRL listed in the entry for the call to complete.
There are some more limiting factors to follow, but they are less common. Let's look at the DMI field next. This will be an arbitrary number that points to another translator that deletes and/or inserts digits to the dialed number. Look at DMI 15.
REQ: prt
CUST:
TYPE: dgt
DMI: 15
DEL 1
INST
CTYP NPA
The first line tells that one digit will be deleted from the first part of the dialed number. Our number started with a 1 after the 9, so this deletes the 1. That probably indicates that the call is being sent out a dedicated long-distance route that doesn't require the 1 at the beginning.
The second line tells what digits will be inserted before the what is left of the number (after deleting the first digit). Nothing is here, so no digits are inserted. If this were going out TIE lines, you might insert digits that tell the system at the other end of the TIE to send the call out a particular set of trunks.
The last line would only be useful on ISDN PRI trunks (Integrated Services Digital Network Primary Rate Interface) to identify the call format as a typical US long distance call.
If any one of the conditions for entry 0 is not met, the call f
alls through to the next entry until it finally matches or runs out of entries.Reach Phil at philruffin@hotmail.com.
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