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August 2008 |
A PoE compliant PSE will not kill a non-PoE device. This is because the PSE will check the receiving end for PoE compliance before supplying power. A compliant PoE powered device at the receiving end has a PoE Signature Resistor for identification. If a device at the receiving end does not have a PoE Signature Resistor, the PSE will not supply power to it.
The checking voltage for Signature Resistor is only 2.8V initially. It is small enough not to kill a networking device.
For example, most laptops if not all as of August 2008 are not PoE compliant. When we connect such a laptop to a PSE, nothing will happen other than a waste of time.
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August 2008 |
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Yes there is. It is because Ethernet Cable is made of copper and copper has a resistamce value that is significant enough to cause the voltage and energy (wattage) of power to drop over a distance. The block diagram below shows the resistance value to be 20Ohm for a cable length of 100 metre.
Suppose PSE sends out 0.35A at 44V = 15.4W
The wattage loss will be 20 x 0.35 x 0.35 = 2.45W
The PD will receive 12.95W
Therefore, if the PD requires 12.95W for operation and if the cable length is longer, the power required will be insufficient.
The block diagram originates from Korenix Technology Company Ltd of Taiwan.
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August 2008 |
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Yes there is. It is because Ethernet Cable is made of copper and copper has a resistamce value that is significant enough to cause the voltage and energy (wattage) of power to drop over a distance. The block diagram below shows the resistance value to be 20Ohm for a cable length of 100 metre.
Suppose PSE sends out 0.35A at 44V = 15.4W
The wattage loss will be 20 x 0.35 x 0.35 = 2.45W
The PD will receive 12.95W
Therefore, if the PD requires 12.95W for operation and if the cable length is longer, the power required will be insufficient.
The block diagram originates from Korenix Technology Company Ltd of Taiwan.
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August 2008 |
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Yes there is. It is because Ethernet Cable is made of copper and copper has a resistamce value that is significant enough to cause the voltage and energy (wattage) of power to drop over a distance. The block diagram below shows the resistance value to be 20Ohm for a cable length of 100 metre.
Suppose PSE sends out 0.35A at 44V = 15.4W
The wattage loss will be 20 x 0.35 x 0.35 = 2.45W
The PD will receive 12.95W
Therefore, if the PD requires 12.95W for operation and if the cable length is longer, the power required will be insufficient.
The block diagram originates from Korenix Technology Company Ltd of Taiwan.
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August 2008 |
Yes we can. Please see the example below. The diagram originates from Planet Technology Corp of Taiwan.
The Switch on 3/F is PoE PSE
The camera on 2/F and 1/F are PoE PD
The computers on 1/F are NOT PoE devices as they have their own power supply
The cameras on G/F are NOT PoE devices as they are old installations
We need to apply a splitter for NON PoE networked devices
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