TWO DIMENSIONAL SWITCHING

Using one type of switch for large network is uneconomical. Hence to build a large network a number of stages are employed using small switches as building blocks. Such a network requires changing both the time slot and highway. Therefore the switching network usually employs both types of switches. Viz.space and time switch. This type of network is known as two dimensional networks. These networks can have various combinations of the two types of switches and denoted as TS. TST. TSST etc.

TST Network

As the name suggests .in a TST network there are two time stages separated by a space stage. The function of time slot changing where as the latter performs highway jumping.

Let us consider a network having 4 input and 4 output highways. Each of the input and output time stages will have n time switches and the space stage will consist of an nxn crospoint matrix. Thus it is possible to connect any time slot in incoming PCM to any time slot in outgoing PCM.

For example let us take only four I/C and outgoing PCM highways as shown below.

There will be four time switches in each T-stages and space switch will consist of 4x4 matrix. let us consider connecting two subscribers through this network. Let us assume central processor assigns TS4 on Hwy0 to the calling party and TS6 on Hwy3 to the called party. The central controller establishes the paths in 3 steps. To introduce greater flexibility it uses an intermediate time slot. TSX which is also known as internal time-slot. The three switching steps for transfer of speech sample of the calling party to the

Step1 Input Time Stage(IT) TS4 Hwy0 to TSx Hwy0 Step2 Space Stage(S) TSx Hwy0 to TSx Hwy3 Step3 Output Time Stage(OT) TSx Hwy3 to TS6 Hwy3

`

As the message can be conveyed only in one direction through this path another independent path to carry the message in other direction is also established as shown in fig.3. The internal time slot for other direction is Tsy.

CONCLUSION

Digital switching has become a synonym for time division multiplex digital switching system. Digital signals are switched in two modes. Viz. time switching and space switching. In a practical digital switch a combination of both is employed to increase the traffic handling capacity of the switch at minimum cost. Among the various possible combinations TST structure is most commonly used.

HWY 0

HWY 1

HWY 2

HWY 3

TIME SWITCH

TS6 ^TSY

TSX

SPACE

SWITCH TIME

SWITCH

TSY

TSX TS6

TS4

HIGHWAYS

SERVICES

INTELLIGENT NETWORK (IN) SERVICES What is "IN" Services?

Bhavnagar Telecom network includes "Intelligent Network" or "IN" SERVICES for its valued subscribers.

This services is so intelligent in giving instant solutions to the needs of the customers, that it is called "INTELLIGENT NETWORK"

(a) Free Phone Service (FPH) (b) India Telecom Card (ITC) (c) Account Card Calling (ACC) (d) Premium Rate Service (PRM) (e) Virtual Private Number (VPN)

• Free Phone Service (FPH)

As the name suggests, the caller can make toll free calls by dialing and advertised Free phone Number. The called number pays full cost of the call. Variously known as "Green Number Services" and "Toll Free Service", it is probably the most popular IN service. It is widely used by business enterprises around the world for providing free product information and help lines. This service becomes all the more powerful when features such as Origin Dependent Routing and Time Dependent Routing are utilized. This means that the calls can be routed to different numbers depending upon the caller's location, calling time.

Free phone service is provided to the IN subscriber on existing telephone connection.

• India Telephone Card (ITC)

The service allows the subscriber to place calls from any DTMF telephone (presently) to any destination number. Local / STD / ISD calls be made from a STD barred telephone also. The cost of these calls is charged to the account specified by ITC number. The telephone number from which the call originated is not charge. The user invokes the service by dialling Account Number after authentication, the allows to dial any destination local or national or international.

• Account Card Calling (ACC)

The customer, who may be a normal telephone subscriber, is given an account number to which all the calls made are credited to a pre determined "credit limit". Call can be made from any telephone after passing the authentication check. The caller is warned of the impending expiry of the credit limit. As opposed to the India Telephone Card Calling Service, which is a debit :Card: service, this is a "Credit" service.

• Premium Rate Service (PRM)

Value added professional information or advice can be accessed by any telephone

government agencies in Jamnagar Telecom District. This number can be accessed from any point in the network. For the same PRM service, the subscriber can opt for multiple destination numbers.

• Virtual Private Network (VPN)

This service allows the subscriber to have his own private network by utilizing the pubic network resources. It is like having PABX with Closed Groups (CUG) and class of service restrictions. A VPN subscriber can define his own dialling and routing plan between all his destination locations and configure them as if they were on a PABX, using the PSTN resources. The VPN locations (PSTN Numbers) can be a part of a CUG or outside it. The CUG members call each other by short codes which are defined in the VPN's Private Numbering Plan.

VPN user can originate calls to other members of their own group (On net to On net) and calls to external public numbers (On net to Off net). They can also make calls into the VPN from external public numbers (Off net to On net) and also use VPN resources from any external public number in the network to call any other external public number (Off net to Off net). Authorization when be required for all the above cases except on net to on net calls. The service allows online modification of authorization code by the user.