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From: goldstein@delni.enet.dec.com (Fred R. Goldstein)
Newsgroups: comp.dcom.telecom
Subject: Re: Answer Supervision on PBX
Message-ID: <14071@accuvax.nwu.edu>
Date: 26 Oct 90 16:24:22 GMT
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X-Telecom-Digest: Volume 10, Issue 767, Message 5 of 8


In article <14004@accuvax.nwu.edu>, dave@westmark.westmark.com (Dave
Levenson) writes...

>In article <13937@accuvax.nwu.edu>, goldstein@delni.enet.dec.com (Fred
>R. Goldstein) writes:

>> >is there any way around the fact that since the school is a 'business'
>> >with a 'business line' the residents of the residence halls who are on
>> >the system must pay for local calls?

>It would be within the tariff to allow the residences to have
>residential rates, while the rest of the campus pays business rates.
>It may not be within the capabilities of the PBX to separate the
>outgoing call traffic into different outgoing trunk groups.  

Now we're getting down to interesting details.  Is it within the
capabilities of System 75 to separate residential from toll traffic?
Can YOUR campus save megabucks?

I ran into this several years ago while consulting to a local college
which I shall not name, except to say that they did not implement my
suggestions for residential service even though they bought the
"right" PBX.  On some PBXs, the automatic route selection interacts
with the toll restriction thusly:

	Take first choice route,
		If available, use it; if access restricted, REORDER
	If first choice not available or access restricted, iterate for
 	 second and third choice routes, etc.

AT&T's then-extant switches, Dimension and S/85, worked that way. I
suspect that S/75 does too (both S/75 and S/85 are now labeled
"Definity").  So if you can't use the cheapest trunk you can't use the
next-cheapest.  Makes sense in a business, right?

Now let's look at the way the SL-1 does it.

	Take first choice route. 
		If available, use it; if not OR access restricted,
	Iterate for second and third choice routes.

Note that classmark restriction doesn't cause reorder, just a
continued scan for more choices.  IF the first choice group for local
calls is a RESIDENTIAL tariff, and if all BUSINESS (non-dorm) lines
are restricted from reaching it, then business calls will overflow to
the second choice, the business-tariff local lines.  That keeps the
residential lines uncontaminated.  Of course, you can restrict the
residential phones from the overflow (business) groups too, to avoid
cost, though it's not a tariff requirement.

FWIW, the Rolm technique is rather different but ends up working more
like the SL-1 than the S/85.  And for all I know, AT&T may have fixed
this; I did the above research in 1984.


Fred R. Goldstein              Digital Equipment Corp., Littleton MA
goldstein@delni.enet.dec.com   voice: +1 508 486 7388

 Do you think anyone else on the planet would share my opinions, let
 alone a multi-billion dollar corporation?