ZyXEL Communications PLA-470 V2 - V3.0.5 Guía de instalación descargar pdf (Pagina 164)

are major components of an electrical network for the PLC signal since they sepa-

rate the public electrical network from the electrical network of a building, of an

apartment, or of a company.

Most meters allow the PLC signal to pass on each side of the electrical network.

Therefore, it is important to correctly configure the PLC local area network encryp-

tion if the interception by a malevolent person of data flowing over the electrical

network is to be avoided.

Electromechanical meters are the oldest ones. These meters, dating from the

seventies, are very frequently encountered in electrical equipment. They allow the

PLC signal to pass on either side of the electrical circuit. Their evaluated PLC signal

attenuation is 20 dB.

Electromechanical meters were gradually replaced during the 1990s by elec-

tronic counters to prevent piracy. These meters, whose piracy is very difficult, are

used for remote meter readings via the EDF network using the very low rate, low

frequency PLC technology. They also allow the PLC signal to be transmitted. Their

evaluated PLC signal attenuation is 15 dB.

Repeaters

Repeaters are devices frequently used in telecommunications to regenerate the data

transmission signal when the distances are too long for the received signal to be

usable by the data transmission devices.

In the case of PLC networks, the electrical network causes attenuations of the

PLC signal (circulation of electrical network components, noises of the connected

devices, quality of the electrical wirings, and so forth) that sometimes make it

impossible to obtain a PLC link between two distant points of the network without

signal repetition.

There are two types of repeaters: passive repeaters and active repeaters. Passive

repeaters regenerate the PLC signal by using two PLC chips relaying the signal from

one chip to the other one. Repeating takes place both at the physical layer and MAC

layer levels. Active repeaters amplify the PLC signal on the electrical wiring without

using another PLC chip to relay the signal. Repeating only takes place at the physi-

cal layer level.

Figure 7.28 gives an example of repeater use.

Few repeaters can be found in stores since the PLC signal can be satisfactorily

broadcast using PLC devices. However, it may be interesting to repeat the PLC sig-

nal to obtain suitable bit rates over the entire electrical network.

The following PLC repeaters are available in stores:

•

Schneider IR LR 1100;

•

Asoka PL8230-2RP (active);

•

Oxance PLT300, PLT320 (active);

•

CMM RPT1-0.

Repeaters 145

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ZyXEL Communications PLA-470 V2 - V3.0.5 Guía de instalación Pagina 164

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