This is Installment 5 of what I've been calling Nortel for Dummies. Don't take the name personally-I'm just trying to help untrained administrators who need a hand getting started.
If you've been following this series of articles, you've learned how to copy an existing digital telephone set and then to make several changes to it. As long as the new set needs the same caller capability as the one you copied, everything should be fine. At times, though, the new set's user has very different needs from the original one. That's when you may find a need to understand the uses of NCOS (Network Class Of Service) and TGAR (Trunk Group Access Restriction).
When you copy a set, you will normally just keep the TGAR and NCOS the same as the one you copied. At times, though, it may become necessary to change one or both of those values to something else. The way you find out that they need to change is often a complaint that the user can't make certain kinds of calls, or (rarely) because the user can make certain kinds of calls but shouldn't. Perhaps the user needs to dial long distance but can't. Or maybe it's international calls or overhead paging that are needed.
In the best of circumstances the Telecom department (or maybe that's just you) will have a simple chart that shows the level of service for each TGAR and NCOS in use. On the other hand, maybe your company is like most I've seen, and no one really knows. There are a couple of ways to find out, and either one takes a good chunk of your time. The first and most complete way is to analyze the system programming. There are several places to look and just when it starts to make sense, you'll find settings that defy logic.
The basic configuration is simple. Each trunk has one or more TARG numbers assigned, and if a telephone set has a matching number in its TGAR, the trunk cannot be accessed directly from that station. (Note: TGAR is the station assignment and TARG is the trunk assignment.) That part is easy, since you can print the trunk routes in overlay 21 to compare the TARG settings to stations you print in overlay 20. The trick will be to learn the use of each of the trunk routes. You can try looking for a name assigned to each of the trunk route access codes (check the ACOD prompt when you list the route). If that doesn't yield enough information, you can place test calls to see which routes are used for different kinds of calls.
The NCOS is more complex to research. The problem is that you have to understand a good bit about how BARS works (Basic Automatic Route Selection uses overlays 86, 87 and 90). Print the NXX (local exchange), NPA (area code) or SPN (special number) in overlay 90 to see which RLI (Route List Index) is used. Print the RLB (Route List Block) in overlay 86 to see the routing rules, including the FRL (usually, but does not necessarily, relate directly to the NCOS) for each routing option. It's too much to attempt to teach this here.
Most readers will be better off trying to find a phone that has the capability wanted and setting the TGAR and NCOS to be the same as that phone. If you really do need to test, you can set your own phone with each potential setting and test. Just keep in mind that the TGAR setting will usually apply only to dialing access codes directly, and the NCOS setting will determine the ability to call numbers through BARS (usually involves dialing 9 or whatever your company uses for outside calls). In some companies, though, the TGAR is used within BARS also, complicating the whole situation.
Also, don't assume that just because phones have different NCOS values that they have different dialing capabilities. I've seen system programming that makes no distinction among any NCOS settings.
Here's a sample chart:
TGAR
0 Any access code (Operator)
1 No access codes
2 2nd floor paging
3 3rd floor paging
4 4th floor paging
5 2nd floor paging + TIE lines
6 3rd floor paging + TIE lines
7 4th floor paging + TIE lines
NCOS
0 No outside calls except 911
1 Local and Toll-free
2 Long distance
3 International
Reach Phil at philruffin@hotmail.com.
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