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SCADA Component:
Communication Network
The Communication Network refers to the communication equipment needed to transfer data to
and from different sites. The medium used can either be cable, telephone or radio.
The use of cable is usually implemented in a factory. This is not practical for systems
covering large geographical areas because of the high cost of the cables, conduits and the
extensive labor in installing them.
The use of telephone lines (i.e., leased or dial-up) is a cheaper solution for systems
with large coverage. The leased line is used for systems requiring on-line connection with
the remote stations. This is expensive since one telephone line will be needed per site.
Besides leased lines are more expensive than ordinary telephone line. Dial-up lines can be
used on systems requiring updates at regular intervals (e.g., hourly updates). Here
ordinary telephone lines can be used. The host can dial a particular number of a remote
site to get the readings and send commands.
Remote sites are usually not accessible by telephone lines. The use of radio offers an
economical solution. Radio modems are used to connect the remote sites to the host. An
on-line operation can also be implemented on the radio system. For locations wherein a
direct radio link cannot be established, a radio repeater is used to link these sites.
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