Planet SGSW-24040 User Manual page 541

The data pairs are used. Since Ethernet pairs are transformer coupled at each end, it is possible to apply DC power to the
center tap of the isolation transformer without upsetting the data transfer. In this mode of operation the pair on pins 3 and 6 and
the pair on pins 1 and 2 can be of either polarity.
When to install PoE?
Consider the following scenarios:
 • You're planning to install the latest VoIP Phone system to minimize cabling building costs when your company moves into
new offices next month.
 • The company staff has been clamoring for a wireless access point in the picnic area behind the building so they can work on
their laptops through lunch, but the cost of electrical power to the outside is not affordable.
 • Management asks for IP Surveillance Cameras and business access systems throughout the facility, but they would rather
avoid another electrician's payment.
Figure 8-1 - Power Supplied over the Spare Pins
Figure 8-2 - Power Supplied over the Data Pins
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User's Manual of SGSW-24040 / 24240 Series