Different methods of providing power to IP Phones

--> IP Phone requires power in order to operate, it can get power from following three methods,

1) Power Cord

--> Local Power Adapter is used to provide the power to IP Phones.

--> This method is used when the switch does not have POE capability.

--> The problem with this method is it does not scale well, if power is lost to the building then IP Phone does not work.

--> We need to have UPS for every Power Cord, but that is not a good option to use.

--> Simple and least used method.

2) Power Injector

--> Power Injector or Mid Span Power is used to provide the power to IP Phones.

--> This method is also used when the switch does not have POE capability.

--> Power Injector contains two ports in which one port is connected to switch and another to IP Phone.

--> Power Injector typically placed in Wired Infrastructure where UPS would be available.

--> Used When we have less number of IP Phones and switch does not have POE capability.

3) POE

--> This is the preferred method to provide power to IP Phones.

--> POE provides the power to IP Phone with the help of ethernet cable using which it is connected to the network.

--> There are three POE standards used to provide power to IP Phones,

i) POE ----------------- 6.3W ( Fast Link Pulse)

ii) 802.3af -------------15.4W ( DC Voltage)

iii) 802.3at-------------30W

--> The Switch can automatically detect whether IP Phone or PC is connected to the switch port by using Fast Link Pulse or DC Voltage.

--> IP Phone Power Calculator can be used to calculate the power required in the switch to provide power to a certain number of IP Phones.

--> To know more about POE, follow my other post here (POE, POE+)

Ref: Cisco

Md.Kareemoddin

CCIE # 54759