Mitel SX 200 DIGITAL Pabx General Descriptions Manual

							Automatic Route Selection and Toll Control
1. GENERAL
introduction1.01This Section contains a comprehensive description of the Auto-
matic Route Selection (ARS) feature of the 
SX-200@ DIGITAL
PABX. Parts 2 and 3 provide the reader with background information on
the North American Numbering Plan and on the routing options offered
to PABX owners by telecommunications companies. A clear under-
standing of these parts is essential in order to fully implement ARS.
The remainder of the document is dedicated to a detailed description
of ARS, which concludes with a description of how an ARS plan is
prepared on paper, with a scenario centering around a fictitious 
com-
paw.Reason for Reissue
1.02This Section is reissued, to provide a description of the opera-
tion and available features of the SX-200 DIGITAL PABX Generic
1002 and Generic 1003. Changes from the previous issue are identified
by change bars.
ARS: General Description
1.03Within this practice references are made to “the customer”, “the
installation company”, and “the user”. These are defined as
follows:
lThe customer is the owner of the SX-200 DIGITAL PABX.
lThe installation company is a company which is authorized by
Mite1 to sell and install SX-200 DIGITAL PABX. This company
works closely with the customers to determine their require-
ments and then installs and programs the system accordingly.
lThe user is a person who makes use of the facilities of the
PABX through oneof the system’s peripheraldevices
(telephone sets).
*
1.04When a trunk call is initiated from within a PABX there are a
number of factors which govern its routing and connection.
They are: (a) route availability, where a route is defined as a collection
of similar trunks within a Trunk Group; (b) cost, when more than one
route exists; and (c) caller’s toll restriction (i.e., whether the caller is
allowed to make such a call, and if so, on what routes).
1.05ARS is a standard feature of the SX-200 DIGITAL PABX, deriving
the answers to these questions automatically every time a
trunk call is initiated, and routing the call accordingly. The process is
totally transparent to the caller; no access code is required, and the
process does not depend on a fixed numbering plan,
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							SECTION MITLSI 09-094-220-NAPage 2 
						

							Automatic Route Selection and Toll Control
2. NUMBERING PLANS
General2.01The ARS feature is universal, insofar as it is compatible wit.hany numbering plan which may be employed by any public
network. It is, however, necessary to understand the numbering plan of
the public network which serves the PABX in order to make full use of
the toll application of the ARS feature.
North American Numbering Plan
2.02The purpose of any numbering plan is to enable any subscriber
in the network to be connected to any other subscriber in the
network. When the North American numbering plan was introduced,
subscribers were assigned a unique digit string comprising a maximum
of 10 digits, compiled as follows:
Area Code613 
-592-2122
Office Code
4Subscriber Number
2.03The area code defines a geographic telephone area; the office
code identifies a central office (CO) within the area; and the
subscriber number identifies a subscriber of the CO.
2.04It was possible to create a distinction between area and office
codes by ensuring that the second digit of the area code was 1
or 0 and the second digit of the office code was any digit in the range
2 through 9. However, as the number of 
COs within each area grew, it
became necessary to augment the supply of office codes by allowing
the second digit of the code to be in the range 0 through 9. This
produced a conflict between area and office codes, a conflict which
was resolved by the introduction of the digit 1 as prefix to all area
codes (e.g., 
l-6 13-592-2 122).
2.05 The prefix digit 1 has now been generally adopted as a toll
prefix in large areas, where toll charges are incurred for calls
made between offices in the same area (e.g., l-256-2122).
2.06In addition to the digit strings described above, there are 
.sets
qf numbers which are reserved for special services, for example
411 for directory assistance. These numbers do not conflict with area
or office codes.
2.07The present North American numbering plan therefore com-
prises digit strings of one, three, seven, eight, and 11 digits.
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							SECTION MITL9109-094-220-NASome examples are:
Operator
0Service Number
411
Local Call592-1111
Toll Call Within an Area
l-256-2222
Toll Call to Another Area
1-416-486-3333
Toll Call Within an Area (NO 1 prefix)
256-2222
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							Automatic Route Selection and Toll Control
3. CALL ROUTING OPTIONS
General ’
3.01Telephone companies offer a number of different methods of
routing calls over the public network (e.g., tie trunks, WATS
lines), each of which has a different cost structure. Correct use of
these trunks can provide substantial savings to the user.
3.02 To determine which routing options are best suited to any
given PABX a traffic survey should be completed by the in-
stallation company prior to installation. The Traffic Measurement and
Station Message Detail Recording features of the SX-200 DIGITAL
PABX allow usage of these routes to be monitored once the system is
installed, in order that their order of selection may be modified as
traffic demands change. This provides the user with the optimum least
cost choices at any time.
3.03The SX-200 DIGITAL PABX supports the following long distance
services:
lDirect Distance Dialing (DDD)
0
Tie Line
aForeign Exchange
lWide Area Telephone Service (WATS)
0Specialized Common Carrier (SCC).
Direct Distance Dialing
3.04Direct Distance Dialing allows telephone users to call subscrib-
ers within the home and international networks without the
assistance of the operator. Connections are completed over standard
trunk routes and are charged on a usage basis at a rate which varies
with distance, time of day, and day of the week. DDD rates are given in
the local telephone directory, or contact the local Telephone Company
for rate information not listed in the directory.
Tie Line Service
3.05 Tie Line Service provides a “tie” between two 
PABXs. The
charge for each tie line is a flat rate charge based on the airline
mileage of the line. Figure 3-l shows a typical tie line connection
between an SX-200 DIGITAL PABX in Ottawa, and an SX-200 DIGITAL
PABX in Toronto.
Foreign Exchange Service (FX)
3.06A Foreign Exchange (FX) Line can be thought of as a tie line
between a PABX and a CO which is located in a telephone area
other than that designated for the PABX. Via an FX Line, the PABX
appears to the distant CO as a local subscriber and is billed accord-
ingly for calls which are placed through that CO. FX lines have two
applications. The first offers a method of reducing telephone cost in
business situations where many toll calls are made to destinations
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							SECTION MITL9109-094-220-NAOTTAWA CO
AREA CODE 613
AREA
CODE 416
-INDICATES TIE LINE
Figure 3-l Typical Tie Line Figure 3-l Typical Tie Line
6451RO AOOBE26451RO AOOBE2which are within close proximity to one another. For example, a com-
pany located in Ottawa which does much of its business with com-
panies located in and around Toronto could benefit from an FX line, as
shown in 
Figure 3-2. The second application allows a company to offer
\
/AREA CODE 613///iAREA CODE 416
INDICATES
- - -FOREIGN
EXCHANGE LINE
645ORO AOlOEZFigure 3-2 Typical Foreign Exchange Line
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							Automatic Route Selection and Toll Control
the use of the FX to its customers so as to permit them to c.all the
company office (the PABX) without incurring toll charges.
Wide Area Telephone Service (WATS)
3.07 The Wide Area Telephone Service is designed to meet the
needs of customers who make or receive a large number of
long distance calls to or from the same geographical region(s) within
the home country. Calls are 
.originated via Outward WATS lines and
received over Inward WATS lines (800 Service). Generally, each such
line is arranged to provide either inward or outward service, but not
both.
3.08WATS divides the country into geographical regions known as
zones. Zones are incremental, numbering 1 through n, from the
home zone. For example, zone 4 provides a WATS subscriber in the
home zone (zone 1) with access to all telephone subscribers in zones
-1, 2, 3 and 4. Likewise, zone n provides a WATS subscriber in the home
zone with access to all telephone subscribers in all zones. Figure 3-3
shows Canadian WATS zones, 1-6, and the zone numbering which is
unique to WATS subscribers with Area Code 613, where 
MITEL Cor-
poration headquarters is located.
3.09The rates for both Outward and Inward WATS are based on the
zone and the hours of service subscribed to by the customer.
6452ROEOFigure 3-3 Canadian WATS Zoning (Zone 1 Being Area Code 613)
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							SECTION MITL9109-094-220-NASpecialized Common Carrier Service (SCC)
3.10Specialized Common Carrier Service, offered by private com-
panies, provides telephone service between major locations at
a rate which may be less than that charged by the telephone com-
panies. The rate is based on monthly subscription plus a usage charge.
Specialized Common Carriers must be approved by local Communica-
tions Regulations, and may not be universally available. Currently, SCC
services are not available in Canada.
3.11The restriction of this service is that some SCC directories are
limited to major locations. Therefore, to avoid additional toll
charges, the SCC company office must be within a local dialing dis-
tance. A typical SCC arrangement is shown in Figure 3-4.
3.12 When a business subscribes to an SCC it is issued with an
account code (normally seven digits). Calls can then be routed
via the company’s office by dialing a digit string similar to that shown
in the following example:
S-745-1234 wait for dial tone, 1234567 305-994-1234
1Trunk
Access
---I- -
AI’7Code
CodeLong
Distance
Number
seeCompany’s
Office
Page 
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							Automatic Route Selection and Toll Contro/-KA0731ROEOFigure 3-4 Typical SCC Arrangement
- - - INDICATES SPECIALIZED COMMON
CARRIER COMPANY LINESPage 9 
						

							SECTION WllTL9109-094-220-NAPage 10