Isdn, Data Communication, The Internet; Isdn; Setting Up A Connection; The Function Of The Proxima Isdn Lite - Bausch Proxima ISDN Lite Manuel D'utilisation

2. ISDN, Data Communication, the Internet

This chapter starts off with a brief explanation of ISDN and the function of the Proxima ISDN Lite. After that, the concept of Data
Communication is described.
1.1

ISDN

The introduction of ISDN (Integrated Services Digital Network) has made it possible to send information in a digital format.
This helps improve speed and reliability. ISDN was set up to integrate the existing speech, data and telex telephone networks
into one network. Apart from this integration, a separate signaling net was added to speed up connection. Establishing a
connection through the PSTN network (telephone net) by modem took about 15 seconds; this has been reduced to just 2 or 3
seconds by using a terminal adapter through the ISDN network.
In ISDN, only one connection is needed for communication devices like faxes, telephones and terminal adapters. An ISDN
device only responds to an incoming call if the call is actually destined for it. For instance, if a call is made by a terminal
adapter, only a terminal adapter will respond; the fax and telephone will not. This is possible because information is sent
along about the kind of telecommunication service. This means a beeping fax on the line is a thing of the past.
With an ISDN2 or BRI (Basic Rate Interface) connection, you have two so-called B channels (64 Kbps) and a D channel (16
Kbps) at your disposal. Both the B channels are data channels, whereas the D channel gives access to the signaling net and
is used to make a connection. It is possible to connect eight ISDN devices to an ISDN2 connection, with a maximum total
cable length of 200 meters between devices and ISDN2 connection.
1.1.1

Setting up a connection

Setting up a data connection through the ISDN network is almost the same as doing so by modem. Once a protocol has been
selected, a number can be dialed using the ATD command. The Proxima ISDN Lite will now establish a connection through
the
D channel. If the same protocol is selected on both sides, a data connection is set up through one B or possibly both the B
channels.
1.2

The Function of the Proxima ISDN Lite

Computers can exchange information, for example by floppy disk, by connecting two RS232 ports or through a network. When
the Proxima ISDN Lite is used, information is exchanged through the RS232 port and the ISDN network.
In a direct connection between two serial ports, it is only possible to bridge a limited distance (approx. 15 meters). The ISDN
network is used to cross greater distances. It is an existing infrastructure which can be used to establish worldwide
connections. The ISDN network is digital which means data may be sent directly from the serial port by means of a protocol.
telephone
Figure 11: Possible ISDN Configuration
Proxima ISDN
fax
Terminal
adapter
junction box
68
PC
ISDN2
connection