The Basic Structure Of Private Automatic Branch Exchange

What is a PABX exchange

In generally the full meaning of PABX is Private Automatic Branch Exchange and in practically it stands for a telephone line exchange that is used for business or the office application  as opposed to one that is also used as a common carrier or Telephone Company that is operates for different kinds of  businesses or for the general public services. PABX system  are used to make connections amongst the internal telephones of a private organization or in the different institutes, Those are generally used for business oriented appliction. The PABX system are also connected with a public switched telephone network through trunk lines. In practicaly it is called PSTN line. As they inter connected telephones,  fax machines, modems, and many other parts, the usual term "extensions" that is given is referred to the ending point on the branch.

(i)Basic Blocks Of The PABX exchange:

The PABX exchange uses normal wire connection for total telecommunication system. But  it also uses optical fiber line for its telecommunication system. The basic block of the PABX exchange is given below

(ii)TNT Input lines

For the PABX exchange  8 input lines are taken from the TNT. These lines are taken on a rent. For each line,  has to pay about 100 taka per line. These lines are the input of the AX controller. For the another 8 lines are used as input lines to the AX controller but those lines are carried to the building through optical fiber.

(iii)AX Controller

AX controller is the major part of the PABX exchange. An AX controller mainly converts the input TNT lines for using in the telecommunication system. There are 12 ONSP card inside the AX controller. This AX controller is made by China. The ONSP cards of the AX controller are divided into 2 parts. 1^st part consists of 3 ONSP cards which has yellow colored input and output lines. 2^nd part consists of 9 ONSP cards which has gray colored output lines.

(iv)ONSP Card

An ONSP card is the major part of the AX controller. An ONSP card can take maximum 4 inputs from outside and give maximum 12/24 outputs from it. 1^st 3 ONSP cards can give 12 output lines each and last 12 ONSP cards can give 24 output lines each. These lines are connected to the telephone sets of different rooms of the varsity through wiring.

(v)ASU

ASU is a supporting device of AX controller. There are 2 ONSP cards in the ASU. These 2 ONSP card can give maximum 24 output lines from it.

(vi)Calculation of Total Number of Lines

Another 300 lines are managed about the same way for the internal communication.

(vii)Maintenance

The total PABX exchange system is maintained by navigator software which is mainly IP based. If any problem occurs then it is solved by this software. If anyone wants to call outside of the system area, then he first calls the member who is sitting in the exchange room. He then makes connection for the desired call. If anyone doesn’t know the called subscribers number, he also calls the exchange room and find the number.