ZyXEL Communications PLA-470 V2 - V3.0.5 Instalační příručka stáhnout pdf (Strana 150)

Although the PLC technology does not use the modulation-demodulation pro-

cess implemented in the modems, we talk about a PLC modem to designate the

device to which the terminals that want to take part in the PLC network are con-

nected.

Unlike Wi-Fi interfaces, which are integrated into the terminals in the form of

boards, the PLC interfaces are not integrated into the terminals. Therefore, the ter-

minal, which is generally a computer, connects to the device that has two interfaces:

one for the connection to the electrical network, and the other one (RJ-45 or USB)

for the connection to the terminal.

The PLC modem, which is the most widespread device in the PLC networks, is

also the easiest to use, since it appears as a standard electrical appliance fitted with a

male receptacle to be connected into an outlet and a USB or Ethernet interface to be

connected to the terminal.

When viewed from the outside, a PLC modem therefore has the two following

interfaces:

•

male receptacle;

•

RJ-45 Ethernet or USB network interface.

The modem generally has three indicators (LED) that indicate the presence of

the 110 to 220V/50 to 60 Hz, PLC signal on the electrical interface and that of the

Ethernet network on the RJ-45 interface to the user (see Figure 7.8, left).

Some devices have up to five indicator lights so that the user can check that the

device is in good working order.

Dissipation in PLC Modems

The first HomePlug 1.0 PLC devices in plastic packages had heat dissipation problems due

to the permanent 110-200V/50-60 Hz power supply. This resulted in failures of the elec-

tronic components that did not withstand heat for long periods in the packages.

The PLC devices have been improved with the emergence of more robust compo-

nents, cooling fins, and vent holes (see Figure 7.8, right) so that they can operate correctly

even in situations in which the devices were stacked or placed in poorly ventilated environ-

PLC Modems 131

Figure 7.8 Outside and inside of a HomePlug Corinex PowerNet PLC modem

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ZyXEL Communications PLA-470 V2 - V3.0.5 Instalační příručka Strana 150