PSTN

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PSTN CPE

• Week 6

ICS 620
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Telephone Network
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Components of The Network

• Phone
• Network Access
• Central Office
• PBXs
• Trunks and Tie Lines

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Subscriber's Loop
On Hook 48 VDC CO Battery
PREMISES
LOOP PLANT
INSIDE WIRE
TELEPHONE
Touch Pad
(TIP)
Central Office
RECEIVER
Ringer 90 VAC
CARBON XMTR
- (RING)
Minimum Point of Entry (MPOE) (Demarc)
Outlet
Off Hook 600-900 Ohm Load
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Network Access

• Local Access and Transport Area
• Local Exchange Carrier (LEC)
• Inter Exchange Carrier
• Cellular Operator
• Competitive Local Exchange Carrier (CLEC)
• Address -- NANP

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View of the Network
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Switch Hierarchy
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New RBOC Configuration

• Verizon (Nynex, Bell Atlantic, GTE)
• Bell South
• Southwestern Bell (SBC), Ameritech, Pacific
  Telesis
• Qwest (U. S. West Qwest)

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Local Access and Transport Area

• Resulted from the Modification of Final Judgement
• Levied on the entire industry
• 198 geographic divisions
• Defines operating areas for franchise holders
• Established rules for conduct of business and
  services authorized

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Local Exchange Carrier

• Provides the end instrument connectivity to the
  national system
• Prior to 1996 intra-LATA communications only
• Regulated by the PUC
• Until 1996, this was monopolistic for the local
  customer

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Inter Exchange Carrier

• Provides the connectivity between LECs
• Prior to 1996 inter-LATA communications only
• a.k.a - the long distance carrier
• Equal access

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Competitive Access Provider

• Competition in the local environment
• Part of Comm Act of 96
• The most volatile area of telephone industry
• CLEC

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Wireless CLECs
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Cellular Operator

• Two in each geographic area
• "A" band -- non-telco operator
• "B" band -- telco operator
• Each has an independently built infrastructure

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Cellular Switching
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PCS Operator

• Seven in each geographic area
• Two are regional
• Five are local
• One is minority owned

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Cellular/PCS Bands
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PCS Footprint
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Address -- North American Numbering Plan

• Developed by Bellcore
• Was NPX-NNX-XXXX
• N 2-9, P 0, 1
• Then NPX-NXX-XXXX
• Now NXX-NXX-XXXX
• International Prefix -- 011

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Central Office

• Main Frame
• Cross connect
• Switching fabric
• Database
• Centrex

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Central Office - Diagram
Public Utility Power
System Admin Terminal
Maint Terminal
UPS
Digital
Modem
Modem
Modem
Administration
Maintenance
Power
Modem Pool
Analog
Program Store
Computer
Central Computer Control (CCC)
Computer to PBX Digital Mux Interface
Call Store
LAN
Proprietary
VF Carrier
Codec
Codec
Analog Lines
Codec
Codec
Codec
Codec
Analog
Analog
Switching Matrix
D Type
Codec
Codec
Trunks
Lines
Digital channel
Digital Lines
Digital
Digital
Digital Facility
CCC Interface
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PBXs

• Premise equipment
• Less trunks than stations
• Rich Feature Set
• Moves, adds, and changes

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PBX Features

• Voice systems generic features and functions
  that are inherent in the majority of PBX and
  digital key systems manufactured today
• Features (in alphabetical order)
• account/authorization codes
• AUTOMATIC CALL DISTRIBUTION
• ANI/DNIS service

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PBX Features - contd

• call forwarding-local/remote
• call park
• call routing plans
• caller id blocking/unblocking
• camp-on
• CLASS-OF-SERVICE (station/trunk)
• conferencing

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PBX Features - contd

• directed call pickup/remote call pickup
• do-not-disturb
• flexible numbering
• intercom
• LEAST COST ROUTING
• music on-hold, paging, background
• PAGING
• recall

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PBX Features - contd

• remote programming and diagnostics
• STATION MESSAGE DETAIL RECORDING
• system repertory dialing
• system security
• TRUNKS ANALOG/DIGITAL
• types EM, DID, T-1/E-1, PRI, loop, ground, DISA
• VOICE PROCESSING

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Trunks and Tie Lines

• Analog --
• EM (wink or immediate), Loop, Ground, DID, DOD
• Digital
• Multiplexing
• Tandem and Toll connections

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PBXs-Peripherals

• Voice processing
• Voice mail
• auto attendant
• interactive voice response
• ACD
• Call sequencing (LCR or ARS)
• System management

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Automatic Call Distribution

• Definition ACD is a system capability that
  allocates incoming trunk calls among agents in a
  programmed group in such a way that each agent
  receives an equitable share of the load.

Cortelco Systems, 1997
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ACD Programming Flow
Ring Command
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Least Cost Routing

• Least Cost Routing (LCR) automatically selects
  the most economical available route for each
  outgoing trunk call. Route selection is based on
  the following factors
• time of day, day of week, destination area code,
  COS of caller and trunk, status of trunk.

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Electronic Digital Key/Hybrids

• Originally designed to take the place of
  mechanical 1A2 systems
• Programmable features
• Modular design/proprietary equipment
• Capable of replicating PBX function

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Review

• Inter Intra Carriers
• Central Offices
• Wireless Switching
• PBXs and Features
• Digital Systems
• Traffic analysis