Digital Telephone Exchange

Block Diagram of Digital Telephone Exchange
Block Diagram of Digital Telephone Exchange

The digital Exchange includes the following Hardware Sub-System.

1- Digital Line Unite (DLU).

The DLU is connected to the LTG and it is responsible for terminating of the Subscriber line and subscriber line traffic. The DLU can be installed locally or remotely, it has the following 4 primary functions.

  1. Conversion of the analog lines to digital.
  2. To accommodate the variable traffic load.
  3. Connection of the sub lines.
  4. ISDN (Integrated Services Digital Network) connected.

2- Line Trunk Group (LTG)

The LTG provides the inter face b/w the Digital Switching Network and the Network environment of the Exchange, which may be digital or analog .it perform the following functions.

  1. Receive and Transmit information of trunk and subscriber lines.
  2. Send Signals and Tones.
  3. Send and Receive messages to and form the CP.
  4. Adopt the transmission format to the 8 Mb/Sec highway of the switching network.
  5. Establish test connections.
  6. Display operating status of the individual module on LED indicator.
  7. Call charge registration.
  8. Detect fault in LTG.
  9. Detect fault on internal exchange interface during call processing.

3- Switching Network (SN)

All types and size of exchanges use the switching Network, The Switching Network establish a connection b/w two subscribers, belong to Different LTG’.The Switching Network also provide connection for message channel, these connections are always in indirect manner due to allow the switches to stand-by position in case of failure one switch.Read More

4- Coordination Processor (CP)

The CP handles the data base as well as configuration and coordination functions, the functions are given below.

  1. Storage of all programs Exchanges and Sub Data.
  2. Connection with Operation and Maintenance Center (OMC).
  3. Handling of the machine interface card. In order to reduce the work load of the CP and to achieve faster processing, some processing functions are distributed over several micro- processors in the digital exchange. These functions are handled by the “CP complex” which consists of the following stages.
  4. Coordination Processor.
  5.  External Memory.
  6. Operation and Maintenance Terminal.
  7. System Panel.
  8. Message Buffer.
  9. Central Clock Generator.

5- Common Channel Signaling Network Control (CCNC)

CCNC is responsible for the transfer of message through a common Signaling Channel b/w Different Exchanges using the CCS7 System.