EWSD "Eidal Widal Switch Digital" is the digital exchange made by German company Siemens.It is used as a local , tandem and transit as well as international gateway exchange.

Structural Units of EWSD Switch:

.Digital Line Unit 

.Line Trunk Group

.Switching Network

.Coordination Processor

Before going into the detail of these i let you people know that every exchange has five parts which are as follows:

1. Power

2. Access

3. Control

4. Switching

5. Signalling 

Now the details of structural unit of EWSD are:

1. Digital Line Unit:

.Provide gateway to EWSD Exchange

.Data of commercial and home subscribers are stores in specific modules in DLU

.Telephone ring is generated in DLU

.Billing is done in this unit

.Provides contact with Digital Interface Unit DIU

2. Line Trunk Group LTG

.It forms the interface between digital environment of the node and digital switch.

.performs non central control function

.provide direct connection through DDF of one exchange with other exchange of same city or other cities.

.It also generate telephone ring

.Provide interface between DLU and DIU.

3. Switching Networks :

.It is used to switch connection of different services like telephony , teletext etc.

.Highly integrated switching networks module

.An exchange of 10000 subscribers may accommodate in a single rack of SN.

4. Coordination Processor :

. It performs following functions in network node like Call Processing , Operation and Maintenance and Safeguarding.

It consist of following Processors.

.Base Processors

.Call Processors

.Input/output control

.Bus for common memory

.Input/output processors

Coordination processor modules are:

.BAP

.CAP

.IOC

.Bus for common memory BCMY

.The Common Memory CMY