Advertisement
1.
INTRODUCTION
The primary function of ISPBX is to provide facilities to make voice communication between
telephone sets possible. In most cases these telephone sets are normal analogue sets where
the speech signal is transformed into an analogue electrical signal and transferred over a 2 wire
twisted pair to the ISPBX, where it is converted into a 64 kbps digital signal. This signal is
switched in digital form to the required destination. The digital signal is then converted back
to analogue form and sent to the destination telephone set. Here the analogue electrical signal
is translated back into an audible signal.
The ISPBX can be connected to other PBXs or to the public switched telephone network with
analogue trunk or tie lines. A speech connection between telephone sets in different PBXs (or
PSTN) uses these trunk or tie lines.
A connection can be made using the ISPBX, from one digital set to another. The same sort of
telephone exchange facilities are then offered for digital connections. Various kinds of
peripherals can be connected.
It is not necessary to install a dedicated data network on a plant for the transfer of digital
information. The digital peripherals can be connected to the ISPBX using the existing
telephone wiring. Alternatively, digital connections can be used.
1.1.
DATA COMMUNICATION
For the transfer of digital information between two digital parties, terminals or peripherals, the
same facilities are available as for voice communication. The ISPBX provides a transparent
path between two ports and the terminals determine what kind of information is transferred
between the terminals and if necessary what type of protocol is used between them.
1.1.1. Data Communication within the ISPBX
A digital connection can be established using analogue lines by using modems. A modem is
connected to an Analogue Line Circuit (ALC) instead of a normal analogue telephone set. The
connection between two data parties is established as if it was a normal speech call. The ISPBX
is not aware that a digital connection has been made.
A purely digital connection is made by connecting the digital peripheral to a Data Terminal
Adaptor which is in turn connected to a Digital Line Circuit (DLC) or a Digital Trunk and
Extension (DTX). A Data Terminal Adaptor is a SOPHO-SET, SOPHO-LAM or LAM. Each
digital peripheral is connected to a port identified by a directory number (DNR). Peripherals
can make contact with each other by dialling the required DNR and if the devices are
2
Advertisement
