Private Automatic Branch Telephone Exchange system PABX provides Telephone switching in an office or hospital. A PCM based PABX provides all the facilities like a public Telephone Exchange (LOCAL EXCHANGE). In large organizations it is normally used her different persons for the Telephone facilities, this is done by installing an PABX in the building the Block Diagram of PCM based PABX is shown in above Fig. Which consist of following main parts.
This section connects the PABX with the local Telephone Exchange the No of lines connected with the local exchange and the No of extensions connected with each line depends upon the design of the PABX.
This section checks the status of the subscriber’s line and provides different tone.
The function of switching matrix is to interconnect any two lines along with any internal signaling wires b/w their controls the most common way of Connecting any two lines together is using switching matrix
The digital Telephone sets, fax machines & other data base equipment are connected to this section.
The analog Telephone lines are connected with this section. The digital to analog & analog to digital conversion is done with the help of codes. The No. of extensions point depends on the design of PABX.