policy of COSMOS (Centrex Facility)
The numbering scheme for Centrex facility ‘city wide’
In this scheme only 8 different-blocks are
possible per Centrex Group and to match these with
block numbers, we can have only 8 distinct levels for
8 levels (2-9) have been allotted to Areas.
For Areas like LNG and SHD, SKN & RHN and
JKP & KB common levels have been kept.
For rest of the areas, separate levels have
total no. of Centrex Group possible will be 1023.
Initially a block of 1000 numbers have been
allotted for each Area Groups for allotment of new
digit number will be used for Internal dialing for
Centrex Group. ‘O’ is used for PSTN access.
Existing customer can opt for this facility in
a group with minimum number of 5 members.
The upper limit of members of a Centrex Group
is 8000 at present.
If a Group falls below 5,
it will automatically
be closed. However, they may continue as PSTN
subscriber with change of numbers.
subscribers/customers can apply for this facility to
CO(COSMOS) under DGM(Comml) HQ in the prescribed form
as enclosed as Annexure II.
They will submit the copy of last paid bill
alongwith the application in original. There will be no signature verification at this stage.
However, in case of a company/Firm the
authorized signatory will apply to CO(COSMOS) for
receipt of application from a Group, the CO(COSMOS)
will allot them a SOC name which can have 3 to 8 alpha
numeric character and a SOC code of six digit.
The first two digits will indicate Area code
and last 4 digit will indicate the Group code
For example, if Punjab National Bank applies
for Centrex Facility, the CO(COSMOS) after
verification of the identity of the authorized
signatory will allot a Group name say ‘PNB’ to the
Bank and if their main branch falls in Central area
then he will have a SOC code like ‘04 0100’
(‘04’ for Area and ‘0100’ for
SOC codes 0000 to 0099 will be reserved for
Areas for Centrex facility within Exchange Area / Wire
a group is formed, any existing/new subscribers can
become the member of the Centrex Group, later by
applying to CO(COSMOS) along with their desired SOC
code and CA No.
A new customer who wants to have a new
connection and also needs Centrex facility will apply
for both NTC and Centrex Facility to CO(COSMOS).
On Application of a Group, the CO(COSMOS) HQ
will issue a single OB both for change of number and
provision of Centrex facility.
every Group will be represented by a Group leader
called Group Co-ordinator.
However, this will not be essential in every
a Group is formed with a Group-coordinator as their
representative, then the co-ordinator can correspond
with MTNL on behalf of the Group for getting the
facility extended to a new subscriber. However, there will be no interference of group co-ordinator
in inclusion/exclusion of any Centrex Group
subscribers. Subscriber is free to enter/exit in Centrex Group.
uniform tariff of Rs.125/- per DEL per month will be
charged for the COSMOS facility.
This would be in addition to the monthly rental
chargeable from the subscriber as per his application
tariff plan. All
intra COSMOS calls shall be free.
bills of the centrex customers will be issued by the
Sales) will be in-charge of all Centrex customers. He
will take care of the requirements of Centrex
customers treating them as CIPs.
Detailed procedure/Flow of OB for NTC, shift,
change of Nos.
billing. FRS, etc. will be issued separately by GM(IT).
CENTREX OF MTNL DELHI(Technology
and Numbering Scheme)
New technology Switch is taken as source switch to
provide the service. It is at JKPD4 with R-25 version.
has major deployment in the network. It forms 41% of
basic services equipment with 27 main exchanges out of
65 and 80 RSUs out of total 144.
has two stage remote switching capability called CSND
and CNE. This provides scope to cover wire-centers
is easy, among all technology, to redeploys line units
(CSND) from one place to another in existing network
mainly due to simplicity and expertise available with
project and maintaince unit as well.
can be any number of Centrex subscribers within the
limit of exchange traffic and connection capacity of
of Centrex group can be 1023.
are eight different blocks possible per Centrex group.
Block number is designated by digit 2 to 9 (1 and 0
are not used. They are used for emergency/special
service and PSTN access respectively)
of Subscriber possible per Centrex group is 8000.
numbering or short code dialing ranges from two to
digit also forms starting digit of internal dialing.
dialing digits, other than block number, are
essentially last digits of PSTN number.
PSTN number is 28823546; Four-digit internal
number for Centrex group is 7546.
– three digits matching with PSTN number (000~999)
– block number (2~9)
28830000 – Head number (ND) for the block 7.
should be in such a way that four digits internal
dialing code tallies with last four digits of PSTN
number. Therefore fifth digit of number is to match
with block number or prefix digit.
and FRS computer system at present can analyse up to
fist four digits only, therefore fourth digit is
chosen to differentiate
area. Care is taken to allot digit that tally with
existing PSTN starting digit. Since due to limitations
of ‘head number’ there can be eight series only,
few geographically co-located area will share same
exchange level though different range of last three
above assumptions following
numbering scheme adopted
Z Y XXX
| | | |
| | | |
| | |
|____Centrex member number ( 000 to 999)
| | |_________ Fifth digit to match with prefix/block.
(2 ~ 9).
This again matches with ‘Z’
| |___________Fourth digit to differentiate GM area(2~9)
2 – LNG(000~499)
3 – East
4 – Central
| 5 – JKP(000~499) & KB(500~999)
6 – BCP
| 7 – SNG(000~499) & RHN(500~999)
| 8 – RG
| 9 –NP
level for MTNL Delhi. Level 289
reserved for expansion.
Based on above
scheme, following are numbering chart for areas
- 28833000 to