Vision System Manual
45
Matrix
Behind the PBX Applications
What’s this?
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.
21
23
28
22
21
23
22
In such situations, it is not easy to implement toll control restrictions.
Consider a simple event
Station 21 of PBX B in the figure above is not given long distance dialing facility. It has access to all the trunks.
Now when he wants to use T2 or T3, which are directly coming from PSTN, he dials ‘0’. He gets PSTN dial tone
and dials the number.
But when he does similar procedure on T1, he gets error tone. Because, in this case when station 21 grabs T1
by dialing a code, he gets dial tone of the PBX A. Now when he again dials ‘0’ to grab PSTN dial tone, PBX
understands it to be a long distance call and since station 21 is not allowed long distance calls, the system
rejects dialing on trunk and gives error tone to station A.
Hence now if station 21 of PBX B is to be allowed external dialing through T1, he should be given long distance
dialing access. If this is done then station 21 may make long distance calls on T2 and T3.
The Vision solves this problem by providing programmable PBX Expansion count for each trunk. This count is
the number of digits to be ignored before toll control check is begun. The PBX Expansion count is same as the
number of PBXs connected between the main PBX and the last subscriber.
In the figure shown, the PBX Expansion count of T1 should be kept 1 and for T2 and T3, it should be kept ‘0’.
CAUTION
For all normal applications, keep this PBX Expansion count to 0 for all the trunks. Otherwise, outside
dialing may be hampered. LCR and SMDR will also be affected.
The Vision supports PBX Expansion count for each trunk.
Summary of Contents for EPABX Vision-206S
Page 5: ...Section 1 Introduction...
Page 6: ......
Page 22: ......
Page 23: ...Section 2 Features and Facilities...
Page 24: ......
Page 212: ......
Page 213: ...Section 3 Appendices...
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