Transcript Slide 1

CENTREX
GENERIC
CUSTOMER PREMISES
Switch
a/k/a
5E
CO
End Office
CENTRAL OFFICE
To LATA Tandem
for routing per PIC
or LPIC
Line Side Card
Station Ports
Analog or
Digital
CENTREX*
Trunk Side Cards
Interoffice trunking
CENTREX*
Does this number
(port) belong to this
CTX group?
Features - Is it
allowed to do what it’s
asking to do?
Calling out – How
many NARs? How
many are active now?
Process the call or
return busy?
DECISIONS*
Incoming call – Look at the
digits. Where do I need to
connect this? (What port?)
Available or busy? Forward?
DECISIONS*
N
A
R
S
Voice mail?
Outgoing call – Look at the
digits. Does it stay here or
leave?
Trunk Side Cards
Interoffice trunking
Local Service
Is it local BellSouth?
Is it local CLEC or toll?
Do I have an empty channel?
Overflow or fast busy?
……………………etc etc etc
Network Access Registers
(NARs) are the gateway
between the private Centrex
and the public switched
network. They are the soft
ware equivalent of lines or
trunks, providing inward,
outward or two-way access.
Internal calls do not use NARs.
To / From other
BellSouth local end
offices
CENTREX & CENTREX PRI
Switch
a/k/a
5E
CO
End Office
CENTRAL OFFICE
with Business Communications Manager
CENTREX PRI
CUSTOMER PREMISES
Line Side Card
Station Ports
Line Side Card
Station Ports
CENTREX*
Trunk Side Cards
Interoffice trunking
DECISIONS*
Trunk Side Cards
A BCM is a small version of a
very intelligent switch. Centrex
numbers for the stations are
carried across a PRI used as 23
tie lines.
The BCM also has features,
voice mail and many advanced
options for call handling, but is
still able to make on-net calls to
other Centrex stations outside
the BCM.
N
A
R
S
INCOMING & OUTGOING CALLS
NARs: Network Access Registers
Trunk equivalents: How many
simultaneous calls are allowed
to/from “outside”
CENTREX & CENTREX PRI
Connecting to a PRI ISDN Compatible Switch
DIAL 9 “OUTSIDE” CALL
CO
FIRE STATION
CITY HALL
NARs
“OUTSIDE LINES”
1 Centrex PRI
CENTREX
1 Centrex PRI
FOUR DIGIT NUMBER CALL
Parks
POLICE
CITY Fiber