Behind The Pbx Application - Matrix Visionpro System Manual

Behind the PBX Application

Many times, small and medium range PBX systems are connected behind some bigger PBX systems. Such
applications are used mainly to expand the existing capacity of the big PBX already in use. Stations coming from
the big PBX are used as trunks of the small PBX. There could also be some PSTN trunks coming directly on the
smaller PBX. Such configurations are known as 'Behind the PBX' application.
In such situations, it is not easy to implement toll control restrictions.
How it works
Consider the following illustration.
21
S1
22
S2
23
S3
Sn
PBX B
PBX-A is connected behind PBX-B. In this 'Behind the PBX' configuration, the Trunk Lines T4, T5, T6 of PBX-B are
connected to the stations (SLT) S4, S5, S6 of PBX-A.
However, Trunk lines T1, T2 and T3 of PBX-A are connected directly to the CO.
In such application scenarios, implementing toll control restrictions for the trunks becomes difficult for PBX-B.
For example: station Number 21 of PBX-B in the above illustration is not allowed the facility of long distance dialing.
It has access to all the CO trunks.
When the user of station 21 wants to access T1, T2 or T3 (which are direct trunks from the CO to PBX-B) the user
dials '0' (or the Trunk Access Code assigned) and gets CO dial tone. When the user dials the number, PBX-B
applies Toll Control.
Similarly, when the user of station 21 tries to grab a trunk T4, T5 or T6 (which are connected to stations of PBX-A)
by dialing Trunk Access Code '0' (or the Trunk Access Code assigned), the user gets the dial tone of PBX-A. This
means, the user of station 21 must dial '0' again (or the assigned Trunk Access Code) to grab CO dial tone of the
T1/T2 trunks connected to PBX-A.
Matrix VISIONPRO System Manual
T1
T2
T3
S4
T4
S5
T5
T6
S6
PBX A
T1
T2
31
S1
32
S2
S3
33
S7
S8
S9
PSTN
108