1.3
INTRODUCTORY TOPICS IN TELECOMMUNICATIONS
3
Figure 1.1
The PSTN consists of local networks interconnected by a long-distance network.
(device). An I/O may be a PC, computer, telephone instrument, cellular/PCS telephone
or combined device, facsimile, or conference TV equipment. It may also be some type of
machine that provides a stimulus to a coder or receives stimulus from a decoder in say
some sort of SCADA
2
system.
End-users usually connect to nodes. We will call a node a point or junction in a
transmission system where lines and trunks meet. A node usually carries out a switching
function. In the case of the local area network (LAN), we are stretching the definition.
In this case, a network interface unit is used, through which one or more end-users may
be connected.
A connectivity links an end-user to a node, and from there possibly through other
nodes to some final end-user destination with which the initiating end-user wants to
communicate. Figure 1.2 illustrates this concept.
The IEEE (Ref. 2) defines a connection as "an association of channels, switching
systems, and other functional units set up to provide means for a transfer of information
Figure 1.2
Illustrating the functions of end-users, nodes, and connectivity.
2
SCADA stands for supervisory control and data acquisition.
Summary :
1.3 INTRODUCTORY TOPICS IN TELECOMMUNICATIONS 3 Figure 1.1 The PSTN consists of local networks interconnected by a long-distance network. A connectivity links an end-user to a node, and from there possibly through other nodes to some final end-user destination with which the initiating end-user wants to communicate.
Tags :
endusers,figure,network,enduser,nodes,node,some,usually,connectiity,other,local,system,stimulus